diff --git a/pkg/labels/labels.go b/pkg/labels/labels.go
index 8025feb67..f29fb290a 100644
--- a/pkg/labels/labels.go
+++ b/pkg/labels/labels.go
@@ -13,8 +13,9 @@ const sep = '\xff'
 
 // Well-known label names used by Prometheus components.
 const (
-	MetricName = "__name__"
-	AlertName  = "alertname"
+	MetricName  = "__name__"
+	AlertName   = "alertname"
+	BucketLabel = "le"
 )
 
 // Label is a key/value pair of strings.
@@ -148,6 +149,72 @@ func Compare(a, b Labels) int {
 	return len(a) - len(b)
 }
 
-type LabelsBuilder struct {
+// LabelsBuilder allows modifiying Labels.
+type Builder struct {
 	base Labels
+	del  []string
+	add  []Label
+}
+
+// NewBuilder returns a new LabelsBuilder
+func NewBuilder(base Labels) *Builder {
+	return &Builder{
+		base: base,
+		del:  make([]string, 0, 5),
+		add:  make([]Label, 0, 5),
+	}
+}
+
+// Del deletes the label of the given name.
+func (b *Builder) Del(ns ...string) *Builder {
+	for _, n := range ns {
+		for i, a := range b.add {
+			if a.Name == n {
+				b.add = append(b.add[:i], b.add[i+1:]...)
+			}
+		}
+		b.del = append(b.del, n)
+	}
+	return b
+}
+
+// Set the name/value pair as a label.
+func (b *Builder) Set(n, v string) *Builder {
+	for i, a := range b.add {
+		if a.Name == n {
+			b.add[i].Value = v
+			return b
+		}
+	}
+	b.add = append(b.add, Label{Name: n, Value: v})
+
+	return b
+}
+
+// Labels returns the labels from the builder. If no modifications
+// were made, the originl labels are returned.
+func (b *Builder) Labels() Labels {
+	if len(b.del) == 0 && len(b.add) == 0 {
+		return b.base
+	}
+
+	res := make(Labels, 0, len(b.base)+len(b.add)-len(b.del))
+Outer:
+	for _, l := range b.base {
+		for _, n := range b.del {
+			if l.Name == n {
+				continue Outer
+			}
+		}
+		for _, la := range b.add {
+			if l.Name == la.Name {
+				continue Outer
+			}
+		}
+		res = append(res, l)
+	}
+	res = append(res, b.add...)
+	sort.Sort(res)
+
+	return res
 }
diff --git a/promql/engine.go b/promql/engine.go
index 14bec5799..cc2739e3e 100644
--- a/promql/engine.go
+++ b/promql/engine.go
@@ -36,9 +36,6 @@ const (
 	maxInt64 = 9223372036854774784
 	// The smallest SampleValue that can be converted to an int64 without underflow.
 	minInt64 = -9223372036854775808
-
-	// MetricNameLabel is the name of the label containing the metric name.
-	MetricNameLabel = "__name__"
 )
 
 // convertibleToInt64 returns true if v does not over-/underflow an int64.
@@ -1021,7 +1018,7 @@ Outer:
 				continue Outer
 			}
 		}
-		if l.Name == MetricNameLabel {
+		if l.Name == labels.MetricName {
 			continue
 		}
 		cm = append(cm, l)
@@ -1059,13 +1056,10 @@ func signatureFunc(on bool, names ...string) func(labels.Labels) uint64 {
 // resultMetric returns the metric for the given sample(s) based on the Vector
 // binary operation and the matching options.
 func resultMetric(lhs, rhs labels.Labels, op itemType, matching *VectorMatching) labels.Labels {
-	// del and add hold modifications to the LHS input metric.
-	// Deletions are applied first.
-	del := make([]string, 0, 16)
-	add := make([]labels.Label, 0, 16)
+	lb := labels.NewBuilder(lhs)
 
 	if shouldDropMetricName(op) {
-		del = append(del, MetricNameLabel)
+		lb.Del(labels.MetricName)
 	}
 
 	if matching.Card == CardOneToOne {
@@ -1077,40 +1071,22 @@ func resultMetric(lhs, rhs labels.Labels, op itemType, matching *VectorMatching)
 						continue Outer
 					}
 				}
-				del = append(del, l.Name)
+				lb.Del(l.Name)
 			}
 		} else {
-			del = append(del, matching.MatchingLabels...)
+			lb.Del(matching.MatchingLabels...)
 		}
 	}
 	for _, ln := range matching.Include {
-		// We always want to delete the include label on the LHS
-		// before adding an included one or not.
-		del = append(del, ln)
 		// Included labels from the `group_x` modifier are taken from the "one"-side.
 		if v := rhs.Get(ln); v != "" {
-			add = append(add, labels.Label{Name: ln, Value: v})
+			lb.Set(ln, v)
+		} else {
+			lb.Del(ln)
 		}
 	}
 
-	return modifiedLabels(lhs, del, add)
-}
-
-func modifiedLabels(lhs labels.Labels, del []string, add []labels.Label) labels.Labels {
-	res := make(labels.Labels, 0, len(lhs)+len(add)-len(del))
-Outer:
-	for _, l := range lhs {
-		for _, n := range del {
-			if l.Name == n {
-				continue Outer
-			}
-		}
-		res = append(res, l)
-	}
-	res = append(res, add...)
-	sort.Sort(res)
-
-	return res
+	return lb.Labels()
 }
 
 // VectorscalarBinop evaluates a binary operation between a Vector and a Scalar.
@@ -1135,27 +1111,17 @@ func (ev *evaluator) VectorscalarBinop(op itemType, lhs Vector, rhs Scalar, swap
 		}
 		if keep {
 			lhsSample.V = value
-			lhsSample.Metric = copyLabels(lhsSample.Metric, shouldDropMetricName(op))
-
+			if shouldDropMetricName(op) {
+				lhsSample.Metric = dropMetricName(lhsSample.Metric)
+			}
 			vec = append(vec, lhsSample)
 		}
 	}
 	return vec
 }
 
-func copyLabels(metric labels.Labels, withName bool) labels.Labels {
-	if withName {
-		cm := make(labels.Labels, len(metric))
-		copy(cm, metric)
-		return cm
-	}
-	cm := make(labels.Labels, 0, len(metric)-1)
-	for _, l := range metric {
-		if l.Name != MetricNameLabel {
-			cm = append(cm, l)
-		}
-	}
-	return cm
+func dropMetricName(l labels.Labels) labels.Labels {
+	return labels.NewBuilder(l).Del(labels.MetricName).Labels()
 }
 
 // scalarBinop evaluates a binary operation between two Scalars.
@@ -1268,29 +1234,24 @@ func (ev *evaluator) aggregation(op itemType, grouping []string, without bool, k
 	}
 
 	for _, s := range vec {
-		var (
-			del []string
-			add []labels.Label
-		)
-		if without {
-			del = append(grouping, MetricNameLabel)
+		lb := labels.NewBuilder(s.Metric)
+
+		if without || keepCommon {
+			lb.Del(labels.MetricName)
 		}
 		if op == itemCountValues {
-			del = append(del, valueLabel)
-			add = append(add, labels.Label{Name: valueLabel, Value: fmt.Sprintf("%f", s.V)})
+			lb.Set(valueLabel, fmt.Sprintf("%f", s.V)) // TODO(fabxc): use correct printing.
 		}
 
 		var (
-			metric      = modifiedLabels(s.Metric, del, add)
+			metric      = lb.Labels()
 			groupingKey = metric.Hash()
 		)
 		group, ok := result[groupingKey]
 		// Add a new group if it doesn't exist.
 		if !ok {
 			var m labels.Labels
-			if keepCommon {
-				m = copyLabels(metric, false)
-			} else if without {
+			if keepCommon || without {
 				m = metric
 			} else {
 				m = make(labels.Labels, 0, len(grouping))
diff --git a/promql/functions.go b/promql/functions.go
index 97d4a520c..0afcfa145 100644
--- a/promql/functions.go
+++ b/promql/functions.go
@@ -117,7 +117,7 @@ func extrapolatedRate(ev *evaluator, arg Expr, isCounter bool, isRate bool) Valu
 		}
 
 		resultVector = append(resultVector, Sample{
-			Metric: copyLabels(samples.Metric, false),
+			Metric: dropMetricName(samples.Metric),
 			Point:  Point{V: resultValue, T: ev.Timestamp},
 		})
 	}
@@ -180,7 +180,7 @@ func instantValue(ev *evaluator, arg Expr, isRate bool) Value {
 		}
 
 		resultVector = append(resultVector, Sample{
-			Metric: copyLabels(samples.Metric, false),
+			Metric: dropMetricName(samples.Metric),
 			Point:  Point{V: resultValue, T: ev.Timestamp},
 		})
 	}
@@ -273,7 +273,7 @@ func funcHoltWinters(ev *evaluator, args Expressions) Value {
 		}
 
 		resultVector = append(resultVector, Sample{
-			Metric: copyLabels(samples.Metric, false),
+			Metric: dropMetricName(samples.Metric),
 			Point:  Point{V: s[len(s)-1], T: ev.Timestamp}, // The last value in the Vector is the smoothed result.
 		})
 	}
@@ -304,7 +304,7 @@ func funcClampMax(ev *evaluator, args Expressions) Value {
 	vec := ev.evalVector(args[0])
 	max := ev.evalFloat(args[1])
 	for _, el := range vec {
-		el.Metric = copyLabels(el.Metric, false)
+		el.Metric = dropMetricName(el.Metric)
 		el.V = math.Min(max, float64(el.V))
 	}
 	return vec
@@ -315,7 +315,7 @@ func funcClampMin(ev *evaluator, args Expressions) Value {
 	vec := ev.evalVector(args[0])
 	min := ev.evalFloat(args[1])
 	for _, el := range vec {
-		el.Metric = copyLabels(el.Metric, false)
+		el.Metric = dropMetricName(el.Metric)
 		el.V = math.Max(min, float64(el.V))
 	}
 	return vec
@@ -331,7 +331,7 @@ func funcDropCommonLabels(ev *evaluator, args Expressions) Value {
 
 	for _, l := range vec[0].Metric {
 		// TODO(julius): Should we also drop common metric names?
-		if l.Name == MetricNameLabel {
+		if l.Name == labels.MetricName {
 			continue
 		}
 		common[l.Name] = l.Value
@@ -357,7 +357,7 @@ func funcDropCommonLabels(ev *evaluator, args Expressions) Value {
 	}
 
 	for _, el := range vec {
-		el.Metric = modifiedLabels(el.Metric, cnames, nil)
+		el.Metric = labels.NewBuilder(el.Metric).Del(cnames...).Labels()
 	}
 	return vec
 }
@@ -375,7 +375,7 @@ func funcRound(ev *evaluator, args Expressions) Value {
 
 	vec := ev.evalVector(args[0])
 	for _, el := range vec {
-		el.Metric = copyLabels(el.Metric, false)
+		el.Metric = dropMetricName(el.Metric)
 		el.V = math.Floor(float64(el.V)*toNearestInverse+0.5) / toNearestInverse
 	}
 	return vec
@@ -414,7 +414,7 @@ func aggrOverTime(ev *evaluator, args Expressions, aggrFn func([]Point) float64)
 		}
 
 		resultVector = append(resultVector, Sample{
-			Metric: copyLabels(el.Metric, false),
+			Metric: dropMetricName(el.Metric),
 			Point:  Point{V: aggrFn(el.Points), T: ev.Timestamp},
 		})
 	}
@@ -443,7 +443,7 @@ func funcCountOverTime(ev *evaluator, args Expressions) Value {
 func funcFloor(ev *evaluator, args Expressions) Value {
 	Vector := ev.evalVector(args[0])
 	for _, el := range Vector {
-		el.Metric = copyLabels(el.Metric, false)
+		el.Metric = dropMetricName(el.Metric)
 		el.V = math.Floor(float64(el.V))
 	}
 	return Vector
@@ -493,7 +493,7 @@ func funcQuantileOverTime(ev *evaluator, args Expressions) Value {
 			continue
 		}
 
-		el.Metric = copyLabels(el.Metric, false)
+		el.Metric = dropMetricName(el.Metric)
 		values := make(vectorByValueHeap, 0, len(el.Points))
 		for _, v := range el.Points {
 			values = append(values, Sample{Point: Point{V: v.V}})
@@ -538,7 +538,7 @@ func funcStdvarOverTime(ev *evaluator, args Expressions) Value {
 func funcAbs(ev *evaluator, args Expressions) Value {
 	Vector := ev.evalVector(args[0])
 	for _, el := range Vector {
-		el.Metric = copyLabels(el.Metric, false)
+		el.Metric = dropMetricName(el.Metric)
 		el.V = math.Abs(float64(el.V))
 	}
 	return Vector
@@ -553,7 +553,7 @@ func funcAbsent(ev *evaluator, args Expressions) Value {
 
 	if vs, ok := args[0].(*VectorSelector); ok {
 		for _, ma := range vs.LabelMatchers {
-			if ma.Type == MatchEqual && ma.Name != MetricNameLabel {
+			if ma.Type == MatchEqual && ma.Name != labels.MetricName {
 				m = append(m, labels.Label{Name: ma.Name, Value: ma.Value})
 			}
 		}
@@ -570,7 +570,7 @@ func funcAbsent(ev *evaluator, args Expressions) Value {
 func funcCeil(ev *evaluator, args Expressions) Value {
 	Vector := ev.evalVector(args[0])
 	for _, el := range Vector {
-		el.Metric = copyLabels(el.Metric, false)
+		el.Metric = dropMetricName(el.Metric)
 		el.V = math.Ceil(float64(el.V))
 	}
 	return Vector
@@ -580,7 +580,7 @@ func funcCeil(ev *evaluator, args Expressions) Value {
 func funcExp(ev *evaluator, args Expressions) Value {
 	Vector := ev.evalVector(args[0])
 	for _, el := range Vector {
-		el.Metric = copyLabels(el.Metric, false)
+		el.Metric = dropMetricName(el.Metric)
 		el.V = math.Exp(float64(el.V))
 	}
 	return Vector
@@ -590,7 +590,7 @@ func funcExp(ev *evaluator, args Expressions) Value {
 func funcSqrt(ev *evaluator, args Expressions) Value {
 	Vector := ev.evalVector(args[0])
 	for _, el := range Vector {
-		el.Metric = copyLabels(el.Metric, false)
+		el.Metric = dropMetricName(el.Metric)
 		el.V = math.Sqrt(float64(el.V))
 	}
 	return Vector
@@ -600,7 +600,7 @@ func funcSqrt(ev *evaluator, args Expressions) Value {
 func funcLn(ev *evaluator, args Expressions) Value {
 	Vector := ev.evalVector(args[0])
 	for _, el := range Vector {
-		el.Metric = copyLabels(el.Metric, false)
+		el.Metric = dropMetricName(el.Metric)
 		el.V = math.Log(float64(el.V))
 	}
 	return Vector
@@ -610,7 +610,7 @@ func funcLn(ev *evaluator, args Expressions) Value {
 func funcLog2(ev *evaluator, args Expressions) Value {
 	Vector := ev.evalVector(args[0])
 	for _, el := range Vector {
-		el.Metric = copyLabels(el.Metric, false)
+		el.Metric = dropMetricName(el.Metric)
 		el.V = math.Log2(float64(el.V))
 	}
 	return Vector
@@ -620,7 +620,7 @@ func funcLog2(ev *evaluator, args Expressions) Value {
 func funcLog10(ev *evaluator, args Expressions) Value {
 	Vector := ev.evalVector(args[0])
 	for _, el := range Vector {
-		el.Metric = copyLabels(el.Metric, false)
+		el.Metric = dropMetricName(el.Metric)
 		el.V = math.Log10(float64(el.V))
 	}
 	return Vector
@@ -664,7 +664,7 @@ func funcDeriv(ev *evaluator, args Expressions) Value {
 		}
 		slope, _ := linearRegression(samples.Points, 0)
 		resultSample := Sample{
-			Metric: copyLabels(samples.Metric, false),
+			Metric: dropMetricName(samples.Metric),
 			Point:  Point{V: slope, T: ev.Timestamp},
 		}
 
@@ -688,7 +688,7 @@ func funcPredictLinear(ev *evaluator, args Expressions) Value {
 		slope, intercept := linearRegression(samples.Points, ev.Timestamp)
 
 		resultVector = append(resultVector, Sample{
-			Metric: copyLabels(samples.Metric, false),
+			Metric: dropMetricName(samples.Metric),
 			Point:  Point{V: slope*duration + intercept, T: ev.Timestamp},
 		})
 	}
@@ -715,10 +715,9 @@ func funcHistogramQuantile(ev *evaluator, args Expressions) Value {
 
 		mb, ok := signatureToMetricWithBuckets[hash]
 		if !ok {
-			el.Metric = modifiedLabels(el.Metric, []string{
-				string(model.BucketLabel),
-				MetricNameLabel,
-			}, nil)
+			el.Metric = labels.NewBuilder(el.Metric).
+				Del(labels.BucketLabel, labels.MetricName).
+				Labels()
 
 			mb = &metricWithBuckets{el.Metric, nil}
 			signatureToMetricWithBuckets[hash] = mb
@@ -753,7 +752,7 @@ func funcResets(ev *evaluator, args Expressions) Value {
 		}
 
 		out = append(out, Sample{
-			Metric: copyLabels(samples.Metric, false),
+			Metric: dropMetricName(samples.Metric),
 			Point:  Point{V: float64(resets), T: ev.Timestamp},
 		})
 	}
@@ -777,7 +776,7 @@ func funcChanges(ev *evaluator, args Expressions) Value {
 		}
 
 		out = append(out, Sample{
-			Metric: copyLabels(samples.Metric, false),
+			Metric: dropMetricName(samples.Metric),
 			Point:  Point{V: float64(changes), T: ev.Timestamp},
 		})
 	}
@@ -811,12 +810,12 @@ func funcLabelReplace(ev *evaluator, args Expressions) Value {
 			continue
 		}
 		res := regex.ExpandString([]byte{}, repl, srcVal, indexes)
-		del := []string{dst}
-		add := []labels.Label{}
+
+		lb := labels.NewBuilder(el.Metric).Del(dst)
 		if len(res) > 0 {
-			add = append(add, labels.Label{Name: dst, Value: string(res)})
+			lb.Set(dst, string(res))
 		}
-		el.Metric = modifiedLabels(el.Metric, del, add)
+		el.Metric = lb.Labels()
 
 		h := el.Metric.Hash()
 		if _, ok := outSet[h]; ok {
@@ -853,7 +852,7 @@ func dateWrapper(ev *evaluator, args Expressions, f func(time.Time) float64) Val
 		v = ev.evalVector(args[0])
 	}
 	for _, el := range v {
-		el.Metric = copyLabels(el.Metric, false)
+		el.Metric = dropMetricName(el.Metric)
 		t := time.Unix(int64(el.V), 0).UTC()
 		el.V = f(t)
 	}
diff --git a/promql/parse.go b/promql/parse.go
index 525efd2ec..039f2da5e 100644
--- a/promql/parse.go
+++ b/promql/parse.go
@@ -911,7 +911,7 @@ func (p *parser) metric() labels.Labels {
 		m = p.labelSet()
 	}
 	if name != "" {
-		m = append(m, labels.Label{Name: MetricNameLabel, Value: name})
+		m = append(m, labels.Label{Name: labels.MetricName, Value: name})
 		sort.Sort(m)
 	}
 	return m
@@ -949,12 +949,12 @@ func (p *parser) VectorSelector(name string) *VectorSelector {
 	// Metric name must not be set in the label matchers and before at the same time.
 	if name != "" {
 		for _, m := range matchers {
-			if m.Name == MetricNameLabel {
+			if m.Name == labels.MetricName {
 				p.errorf("metric name must not be set twice: %q or %q", name, m.Value)
 			}
 		}
 		// Set name label matching.
-		m, err := NewLabelMatcher(MatchEqual, MetricNameLabel, name)
+		m, err := NewLabelMatcher(MatchEqual, labels.MetricName, name)
 		if err != nil {
 			panic(err) // Must not happen with metric.Equal.
 		}
diff --git a/promql/printer.go b/promql/printer.go
index 56fab7a9c..969043c95 100644
--- a/promql/printer.go
+++ b/promql/printer.go
@@ -20,6 +20,7 @@ import (
 	"time"
 
 	"github.com/prometheus/common/model"
+	"github.com/prometheus/prometheus/pkg/labels"
 )
 
 // Tree returns a string of the tree structure of the given node.
@@ -216,7 +217,7 @@ func (node *VectorSelector) String() string {
 	labelStrings := make([]string, 0, len(node.LabelMatchers)-1)
 	for _, matcher := range node.LabelMatchers {
 		// Only include the __name__ label if its no equality matching.
-		if matcher.Name == MetricNameLabel && matcher.Type == MatchEqual {
+		if matcher.Name == labels.MetricName && matcher.Type == MatchEqual {
 			continue
 		}
 		labelStrings = append(labelStrings, matcher.String())
diff --git a/promql/quantile.go b/promql/quantile.go
index c7c905460..91f41566d 100644
--- a/promql/quantile.go
+++ b/promql/quantile.go
@@ -17,7 +17,6 @@ import (
 	"math"
 	"sort"
 
-	"github.com/prometheus/common/model"
 	"github.com/prometheus/prometheus/pkg/labels"
 )
 
@@ -26,8 +25,8 @@ import (
 // excludedLabels are the labels to exclude from signature calculation for
 // quantiles.
 var excludedLabels = []string{
-	model.MetricNameLabel,
-	model.BucketLabel,
+	labels.MetricName,
+	labels.BucketLabel,
 }
 
 type bucket struct {