Shakespeare uses extended metaphor in Macbeth's dialogue with the murderers in Macbeth.
In Act 3, Scene 1, when Macbeth interviews his murderers for hire, the murderers affirm that they are men. To which Macbeth wittily replies:
Ay, in the catalogue ye go for men;
As hounds and greyhounds, mongrels, spaniels, curs,
Shoughs, water-rugs and demi-wolves, are clept
All by the name of dogs.
Macbeth's use of extended metaphor in these lines reveals his cautious appraisal of Banquo's would-be murderers. The direct comparison between men and dogs suggests Macbeth's shrewd belief that men, like dogs, are not all created in equal respects; just as there are various breeds of dogs, so are there variations among men.
Macbeth continues his extended metaphor as he derives addtional meaning from the comparison. Some dogs have special talents or gifts "which bounteous nature Hath in him closed", and Macbeth hopes that his murderers-for-hire, like the dogs, have the gift of the "subtle" and "the hunter."
Shakespeare used symbolism in lines 62-63 in Act 3 Scene 1 ofMacbeth.
" Upon my head they placed a fruitless crown,/ and put a barren sceptre in my grip."
The fruitless crown and barren sceptre symbolize Macbeth's impotency and add to the prediction that he will not have son succeed him as king.