Daniel 10:13 ...Then Michael, one of the chief princes, came to help me, because I was detained there with the king of Persia.
Daniel 10:21 ...(No one supports me against them except Michael, your prince.)
Daniel 12:1 At that time Michael, the great prince who protects your people, will arise. There will be a time of distress such as has not happened from the beginning of nations until then. But at that time your people everyone whose name is found written in the book will be delivered.
Jude 9 But even the archangel Michael, when he was disputing with the devil about the body of Moses, did not dare to bring a slanderous accusation against him, but said, The Lord rebuke you!
Rev. 12:7-8 And there was war in heaven. Michael and his angels fought against the dragon, and the dragon and his angels fought back. But he was not strong enough, and they lost their place in heaven.
So Michael is a very powerful archangel who fights against the devil and demons (fallen angels) and succeeds.