Michael was almost identical to Satan; the only difference being Michael had a glowing halo, having served right alongside him as the left and right hands of God. They had twelve large white wings, bright blue eyes, and blonde hair. While on Earth they wore a grey suit, however in battle they had large gold and magenta battle armor and carried a scepter-like weapon.
Being an Archangel who worked so closely to God alongside Satan, it can be assumed they shared the same powers such as flight, telepathy, force fields, near immortality, mind manipulation and to fire massive bolts of energy from their hands. When flying into combat Michael weilds a large scepter like weapon. Being God's second in command it's likely they had many more abilities.
Michael is loyal to God, wholy devout and followed his every word. As such, they hold demons and similar beings in contempt. They do not seem to have an opinion of humanity unless it suits God, more than willing to kill them if they prove to be useless.
Michael acted behind the scenes most of the time and their first appearance had them observing Lan Asuka and Masato Fudo during their discussion about Angels. While they are starting to get suspicious, Michael did not think there they would be a problem. By the time demons started appearing out of Hell, Michael used their influence to start several forms of nuclear warfare to wipe them out while revealing themselves to Masato. Finally, Michael on their mount confronted Satan and Devilman's army and fought against them.