Seemingly Michael of the Old Testament is the same as Michael of the New Testament. Known as being of the greatest or highest class of angels: archangel = great messenger. Saint Michael = Holy One, Who Is Like God? Archistrategos = Highest Heavenly Commander. Biblically the protector of Israel and leader of heaven's armies against the corrupt angels, thusly the images of Michael slaying dragons or serpents. Aquinas concluded that each angel was a species unto itself and thusly not human. Angels are commonly thought to have no physical bodies which gives them advantages and disadvantages in comparison to humans. This would make the various representations of Michael in painting and sculpture nothing but imagery that symbolizes aspects of Michael's spiritual being. There are less established or widespread traditions about who Michael is and what he does. Some significant Protestants viewed Michael as identified with the Logos, a pre-incarnate Christ who will be the one that battles Satan in the end times.

Otherwise there is not a lot known about who archangels are and where they (or angels of any sort) fit in the scheme of creation. I don't think that God would allow centuries of Christians across the Earth to be misled about who the angels are. Much may be hidden but what little is revealed is not generally misleading. Any one claiming to have special knowledge about the Archangels, implying that they have sources superior to the Word of God, is 'like unto' the Gnostics of old. One of the many esoteric teachings about some long hidden truth behind Christianity could turn out to be real, but since the time the Temple curtain was split open, the Way, Truth and Life has stood at our door knocking, lighting lampstands, calling us out. Many have answered without any special knowledge.