Final answer:
Malcolm lists his vices to Macduff as a test of his loyalty and to see if Macduff will support him as the rightful successor to the throne.
Step-by-step explanation:
During the conversation between Malcolm and Macduff, Malcolm speaks at length about his vices. He names several faults, including greed, lust, and deceit. He lists them to Macduff as a test of his loyalty and to see if Macduff will support him as the rightful successor to the throne.