A list of the things Michael is said to do:
He is the only one who stands firm with Gabriel and helps him: "Yet there is no one who stands firmly with me against these {forces} except Michael your prince." Daniel 10:13, 21
He arises in a time of distress such as has never been before, likely the time of the end: "Now at that time Michael, the great prince who stands {guard} over the sons of your people, will arise. And there will be a time of distress such as never occurred since there was a nation until that time; and at that time your people, everyone who is found written in the book, will be rescued." Daniel 12
He disputed with the Devil over Moses' body: "But Michael the archangel, when he disputed with the devil and argued about the body of Moses, did not dare pronounce against him a railing judgment, but said, "The Lord rebuke you!" Jude 9
He and his angels throw Satan out of heaven: "And there was war in heaven, Michael and his angels waging war with the dragon. The dragon and his angels waged war," Revelation 12
Christ descends with his voice: "For the Lord Himself will descend from heaven with a shout, with the voice of {the} archangel and with the trumpet of God, and the dead in Christ will rise first." 1 Thessalonians 4:16
If we believe the Christ is God, one third of a Trinity, then he cannot be Michael. (Though some Trinitarians do argue that he is so I leave it open.)
But if we believe the Christ to be the Son of God, his first born creation but not a part of a Trinity Godhead, then to me it seems reasonable to conclude that Michael may just be the Christ prior to his coming to earth as a man.
Sabrina