What is an important theme in Macbeth and what motifs support it?Quotes would be cool, if you could add some.

One of the major themes in the play has to do with
Macbeth's ambitious desire for power.  He understands that it is morally wrong to kill
and perform other ill acts to attain power; however, Macbeth convinces himself that he
must press forward to get what he wants.  At the beginning of Act 2, Macbeth
hallucinates the dagger which is a motif for the sense of fear and guilt that Macbeth
feels over his plan to murder King Duncan.  In his soliloquy, Macbeth says, "A dagger of
the mind, a false creation, proceeding from the heat-oppressed brain?" (II.i.38-39). 
Later in the play while all are at the banquet and Macbeth hallucinates Banquo's ghost,
Lady Macbeth refers to the "air-drawn dagger" because Macbeth is again expressing his
guilt over having murdered to satisfy his greed and ambition.