Final answer:
The witches in Macbeth speak in rhyming couplets to highlight their supernatural nature, emphasize their mystical powers, and create an eerie atmosphere.
Step-by-step explanation:
The witches in Macbeth speak in rhyming couplets instead of iambic pentameter, like the other characters, for several reasons.
First, it highlights their supernatural nature and otherness, setting them apart from the human characters.
Second, it emphasizes their mystical powers and prophetic abilities, suggesting their connection to the supernatural realm.
Finally, it creates an eerie and unsettling atmosphere, adding to the overall sense of unease and foreboding in the play.