How does Shakespeare use Macbeth's first words to emphasize an important theme in this play?

Many of the plays themes have to do with paradox and equivocation. What is considered "good" and "bad" get swallowed into the chaos of Macbeth's world. It is fitting that Macbeth speaks these lines just before he sees the witches. The witches will welcome him into this world of equivocation and chaos where riddles are designed to be Macbeth's undoing.