Michael didn't need to sleep, yes, even when he was using Dean as a vessel.

However despite this, he watched you every night do your bedtime routine, get into bed, and he followed suit by changing down into boxers, and holding you as you rested against him.

The archangel played with your hair, fingers brushing up against the soft flesh on your cheek, his lips brushing against your head. "Are you still awake, sweetness?"

His voice was low, as to not scare you, despite his reputation.