One of Shakespeare's most famous figures of speech can be found in this scene, when Lady Macbeth says that she fears that her husband has too much of the "milk of human kindness" in him. This is one of many of Shakespeare's figures of speech that has made it into common use in the English language.
There is also foreshadowing. When we discover that Duncan is coming to the Macbeths' castle, Lady Macbeth says that
The raven himself is hoarse
That croaks the fatal entrance of Duncan
Under my battlements.
The audience can strongly suspect at this point that Duncan will not be leaving the castle alive, and that the Macbeths are about to begin their play for the crown.
Finally, Lady Macbeth uses an analogy when she encourages her husband to behave as an "innocent flower" that nevertheless has a "serpent under't" when he greets Duncan.