"unseamed him from the nave to the chop"
This metaphorical language illustrates Macbeths appearance by being ruthless. Alternatively, it suggests how Macbeth is at second nature with his murderess manner which could make the audience question whether Macbeth enjoys this gruesome level of gruesome killing, and perhaps he even enjoys it giving the fact that he "unseam[ingly]" does it.
the phrase 'nave to the chop' creates an imagery of a slaughterer and this raises the query whether Macbeth loves cutting into people and similarly treat them like a piece of meat. From that, I fell that this may reveal they realty/foreshadow Macbeth and show parts of his murderess desire.
the first imagery you take from it, is how brave and clever Macbeth is. Although, the reality is that Macbeth's ambition for death has always been there from the outlet.
