Of course this is a highly interesting part of the play as we focus on Macbeth's disintegration as a moral character and a tragic hero just before he goes to commit the grave crime of regicide - the killing of a King. It is well worth examining this complex soliloquy as a whole and analysing it bit by bit, but as "brevity is the soul of wit" (to quote another Shakespeare play), how about considering the following examples of metaphors in this speech and then using them as a basis for re-reading it and analysing it further yourself.
Consider this following example:
Art thou not, fatal vision, sensible
To feeling, as to sight? or art thou but
A dagger of the mind, a false creation,
Proceeding from the heat-oppressed brain?
Here Macbeth uses metaphors to debate the nature of this vision - he calls this dagger a "fatal vision", and then "a dagger of the mind" suggesting that his evil thoughts in contemplating the murder of his King are being somehow expressed psychologically by his "heat-oppressed brain."
Hope this helps get you started. You will want to examine the part of this speech when Macbeth refers to night and "Nature seems dead". Good luck!