The witches can be interpreted in several ways. They can represent the forces of evil that lead Macbeth astray. They can also be seen as a symbol of Macbeth's inner turmoil. Ultimately, the witches serve as a catalyst for the events that unfold in the play.
By showing Macbeth through the eyes of the witches, Shakespeare creates a sense of mystery and suspense. The audience is given a glimpse into Macbeth's dark side before they even meet him. This makes Macbeth a more complex and interesting character.