Who is Michael Archangel?
In Orthodoxy, Michael is known as Saint Michael the Archangel or Saint Michael the Taxiarch, and in Judaism, Christianity, and Islam, he is known as Archangel Michael. The oldest known allusions of his name are in Jewish literature from the 3rd and 2nd centuries BCE, typically but not necessarily apocalyptic, in which he is described as the chief of the angels and archangels and as the guardian of Israel.
Second Temple Jewish writings
The Book of Enoch, a Jewish apocalypse from the third century BCE, contains the oldest surviving mention of Michael. He is listed as one of seven archangels (the others are Uriel, Raguel, Raphael, Sariel, Gabriel, and Remiel) who “stand ready and enter before the glory of the Lord,” according to the Book of Tobit, a slightly later book.
Almost all Jewish traditions about Michael were adopted by Christianity. The seven Jewish archangels (or four, depending on the tradition, but always including Michael) were associated with the branches of the menorah, the sacred seven-branched lampstand in the Temple, as the seven spirits before God’s throne, as recorded in John 4:5. (“From the throne came flashes of lightning, and rumblings and peals of thunder, and before the throne were burning seven torches of fire, which are the seven spirits of God” - ESV).