The Porter is a drunk gatekeeper who, minutes after the murder, pretends to be the porter of hell, and turns Macbeth's castle into hell's gate.

He appears only at the start of Act 2, Scene 3, speaking in prose while the knocking from Act 2, Scene 2 goes on.

"If a man were porter of hell gate, he should have old turning the key." (Act 2, Scene 3). The joke is closer to the truth than he knows: a man has just damned himself inside.
"here's an equivocator, that could swear in both the scales against either scale" (Act 2, Scene 3). An equivocator lies by telling half-truths. The Globe links this to Henry Garnet, a Catholic priest executed for his part in the Gunpowder Plot after trials held in early 1606: his defence of equivocation was badly damaging to him.

Bradley wrote: "The Porter does not make me smile: the moment is too terrific". Use the Porter as a symbol (the castle as hell), as a mouthpiece for equivocation linking to the Witches and to Macbeth's "equivocation of the fiend" (Act 5, Scene 5), and as a structural contrast whose comedy tightens the tension before the body is found.

The Porter is a drunk gatekeeper who, minutes after the murder, pretends to be the porter of hell, and turns Macbeth's castle into hell's gate.

He appears only at the start of Act 2, Scene 3, speaking in prose while the knocking from Act 2, Scene 2 goes on.

"If a man were porter of hell gate, he should have old turning the key." (Act 2, Scene 3). The joke is closer to the truth than he knows: a man has just damned himself inside.
"here's an equivocator, that could swear in both the scales against either scale" (Act 2, Scene 3). An equivocator lies by telling half-truths. The Globe links this to Henry Garnet, a Catholic priest executed for his part in the Gunpowder Plot after trials held in early 1606: his defence of equivocation was badly damaging to him.