The Witches' Prophecies and False Security
The three witches give Macbeth a series of prophecies that seem to guarantee his safety, but they're actually setting him up for a fall. First, they warn him to "Beware Macduff! Beware the Thane of Fife!" through an armoured head, giving him a clear enemy to fear.
The second prophecy comes from a bloodstained child, telling Macbeth that "none of woman born shall harm Macbeth." This makes him feel invincible because surely everyone is born from a woman, right? Wrong - this is where Shakespeare gets clever with the wording.
The final prophecy promises that "Macbeth shall never vanquished be, until Great Birnam wood to High Dunsinane hill shall come against him." Macbeth thinks this is impossible because forests can't move. His overconfidence in these prophecies becomes his biggest weakness.
Each prophecy appears with a different symbolic image - the armoured head, bloodstained child, and crowned child with a tree. These aren't random; they're clues about how each prophecy will actually come true.
Key Point: The witches' prophecies are deliberately misleading - they're technically true but not in the way Macbeth interprets them.