The spirit creature called Michael is not mentioned often in the Bible. However, when he is referred to, he is in action. In the book of Daniel, Michael is battling wicked angels; in the letter of Jude, he is disputing with Satan; and in Revelation, he is waging war with the Devil and his demons. By defending Jehovah's rulership and fighting God's enemies, Michael lives up to the meaning of his name—"Who is Like God?" But who is Michael?The first sentence is correct. St. Michael is a spirit creature and he is only explicitly mentioned four times in the Bible. In the past St. Michael came to the Archangel Gabriel's aid [(1) Dan 10:13] and quarreled with Satan over St. Moses' body [(2) Jude 9]. In the future (probably in the early 24th century [Dan 9:24,27; Mt 24:37]), St. Michael will stand up on behalf of God's children when the Antichrist appears [(3) Dan 12] and throw him to the ground when he tries to ascend to Heaven [Dan 8:25] and become victorious over Satan in a battle in Heaven [(4) Rev 12:7]. St. Michael may be the cherub who kept vigil at the gates of Eden (the terrestrial paradise where the curse of original sin entered the world with the serpent's help) [Gen 3:24]. He could also be the angel who killed 185,000 troops in the Assyrian King Sennacherib's army in their sleep [2 Ki 19:35], the angel who stood in Balaam's way [Nu 22:22], and the angel through whom God decided to publish the Ten Commandments.
At times, individuals are known by more than one name. For example, the patriarch Jacob is known as Israel, and the apostle Peter, as Simon. (Genesis 49:1,2; Matthew 10:2) Likewise, the Bible indicates that Michael is another name for Jesus Christ, before and after his life on earth. Let us consider Scriptural reasons for drawing that conclusion.
Archangel. God's Word refers to Michael "the archangel." (Jude 9) This term means "chief angel." Notice that Michael is called the archangel. This suggests that there is only one such angel. In fact, the term "archangel" occurs in the Bible only in the singular, never in the plural. Moreover, Jesus is linked with the office of archangel. Regarding the resurrected Lord Jesus Christ, 1 Thessalonians 4:16 states: "The Lord himself will descend from heaven with a commanding call, with an archangel's voice." Thus the voice of Jesus is described as being that of an archangel. This scripture therefore suggests that Jesus himself is the archangel Michael.St. Basil the Great of Caesarea (Church Doctor), Salmeron, and Cardinal St. Robert Bellarmine (Church Doctor) believed that St. Michael is the single highest angel, whereas St. Aquinas (Church Doctor) ranks him as the prince of the lowest angelic order, the angels. In any case, there are actually seven archangels [Tobit 12:15] and so St. Michael is not the only archangel. "The" (definite article) is used in Jude 9 simply because St. Michael is one particular archangel out of several (implied by the indefinite article "an" in 1 Thess 4:16 and explicitly stated in Dan 10:13 and Tobit 12:15). St. Michael does not rebuke demons but leaves that responsibility to the Lord [Jude 9], and Jesus is the Lord Who fulfills that role [Mt 12:28; Mk 1:34]. Why does the writer call Jesus Lord in the penultimate sentence if the Lord is one [Dt 6:4] and Jesus is supposedly not God? Of course, he is forced to because he must submit to St. Paul's teaching that Jesus Christ is Lord [1 Cor 8:6]. Since Jesus Christ is Lord, the Father is Lord, and there is only one Lord [Is 45:5-6], then Jesus and the Father are truly one [Jn 10:30] in the sense of being consubstantial (of the same substance, of the same essence) and therefore just as the Father is God, Jesus is God. Since God was not created and Jesus is God, Jesus is not a creature! Since Jesus is not a creature and St. Michael is a spirit creature, Jesus is not St. Michael the archangel! Now, Jesus is omniscient, as is the plain meaning of Colossians 2:3's affirmation that in Jesus "are hidden all treasures of wisdom and knowledge." Since Jesus is omniscient and no angel is omniscient, Jesus is not St. Michael the archangel! The rhetorical question of Heb 1:5—"to which of the angels did He ever say: 'You are My Son; today, I have become Your Father'?"—has the answer "none." Heb 1:6 says, "Let all God's angels worship Him." Worship in the sense of latria is to be paid to God alone, not an angel who is a creature and not Creator, so Jesus is to be worshiped as God by all the faithful. Now the writer, by virtue of being a Jehovah's Witness, professes that Jesus is Lord by his participation in the divine dominion as God's first and foremost creature, but this does not suffice. Since God alone naturally (not by grace) possesses the glory of happiness, one cannot call any creature "the Lord of glory." God, "The Lord of mighty deeds, He is the king of glory" [Ps 23:10] and so when 1 Cor 2:8 says "had they known, never could they have crucified the Lord of glory," He who was crucified is God, and so Jesus is God, thus Jesus is not a creature, thus Jesus is not St. Michael the archangel.
According to St. Thomas Aquinas's Summa Theologica We can carefully say that Christ as man is creature when "man" is added as a predicate in the reduplication covering the term signifying the nature and not the suppositum. Christ is incorporeal and impassible in his Godhead and is corporeal and passible in His manhood . Contrary to the heretical teaching of Nestorius, St. John Damascene speaks the truth of the Catholic Faith when he says Christ has but one hypostasis (suppositum) which is uncreated in its Godhead and created in its manhood.
Army Leader. The Bible states that "Michael and his archangels battled with the dragon … and its angels." (Revelation 12:7) Thus, Michael is the Leader of an army of faithful angels. Revelation also describes Jesus as the Leader of an army of faithful angels. (Revelation 19:14-16) And the apostle Paul specifically mentions "the Lord Jesus" and "his powerful angels." (2 Thessalonians 1:7; Matthew 16:27; 24:31; 1 Peter 3:22) So the Bible speaks of both Michael and "his angels" and Jesus and "his angels." (Matthew 13:41) Since God's Word nowhere indicates that there are two armies of faithful angels in heaven—one headed by Michael and one headed by Jesus—it is logical to conclude that Michael is none other than Jesus Christ in his heavenly role.*The above replies conclusively prove that Jesus cannot be an angel in the first place, much less St. Michael the archangel.
*More information showing that the name Michael applies to God's Son is found in Volume 2, pages 393-4, of Insight on the Scriptures, published by Jehovah's Witnesses.