The theme of appearance vs. reality shows up throughout Macbeth. One of the earliest references to this is when Macbeth and Banquo encounter the weird sisters (three witches) at the very beginning of Act I. They are unsure of what they see and are wondering if they could be dreaming or imagining their presence in front of them. One of the most striking depictions of this theme would be the banquet scene in which Macbeth believes that the ghost of Banquo has taken a seat at the table, taunting (or at least, reminding Macbeth of his bloody deeds) Macbeth. Finally, as the play comes to a close, Birnam wood is actually marching...or is it? The soldiers are disguised with branches and leaves and it appears as though the prophecy is coming true! There are countless references to things not being what them seem throughout Macbeth. This includes friendships...
“Nothing is / But what is not” (1.3. 131) seems to be one of the most direct statements of Macbeth concerning the theme of appearance vs. reality. Macbeth says this as an aside in trying to figure out what the witches mean by their predictions, and this follows his (near) repetition of the witches’ chant concerning “fair and foul” that equivocates the meaning of those otherwise contrasting words. He immediately fears the evil that he might do to become King (“why do I yield to that suggestion / Whose horrid image doth unfix my hair”). What he fears at this moment is what he might do, not what he has done—he hasn’t killed Duncan (appearances) but secretly knows the guilt of doing so (reality).
Appearance and reality is an extremely important theme from the play. The first example we see is in Lady Macbeth's plans to murder Duncan. She dictates to Macbeth, look like the innocent flower, But be the serpent under't. (I.v.75) Lady Macbeth knows that Macbeth needs instruction in how to maintain the appearance of innocence as he plots and executes Duncan's murder (she believes he has a weaker "nature" than she does); the reality of the situation is that Lady Macbeth and Macbeth have murderous intents, so Macbeth may take over the crown. After the murder, Macbeth appears to be horrified and devastated by the crimes when, in reality, he is the perpetrator.
As the play continues, Macbeth continues to maintain false appearances. He portrays himself as a loyal friend to Banquo while he secretly plans his murder. Most kinsmen believe Macbeth to be a strong, loyal, intelligent, virtuous ruler who has earned his titles through his merit while the reality is that Macbeth has violently and dishonestly moved up in rank after his last earned title of Thane of Cawdor. One major lesson to be learned from Macbeth: things are almost never how they appear!