Holy Oil

A circle of burning holy oil is the best way to trap an angel. The angel will not be able to leave the circle. It should be noted that a circle of holy fire is not the equivalent to a devil's trap. When in the circle, the angel still has use of their abilities and are able to move, they merely choose not to leave the circle out fear of touching the holy fire. If an angel touches holy fire then not only will the human vessel be destroyed and die, the angel will be killed as well. Michael however is resistant to the holy fire and couldn't be killed by it. Most likely as he's the most powerful Archangel of all.