Many Christians believe that the Michael who appears in the Bible is Christ. They don’t believe that Jesus is an angel, because Michael is never actually called an angel in the Bible; He’s only called the archangel.

I believe that this archangel Michael is one of the ways that Jesus appeared to people, especially in the Old Testament. Here are some Scriptures that lend to this belief. The Bible tells us that it is Michael who intercedes for God’s people in Daniel 12:1. Jesus is also known as our Intercessor. When this archangel—the general of the Lord’s army—appeared to Joshua, Joshua took off his shoes and worshiped him.

We also read in the book of Jude that it’s Michael who resurrects Moses. And of course, Jesus is the Resurrection. We also read that the Lord is going to descend with the voice of the archangel, and we know clearly that Jesus is the one who’s going to descend.

Keep in mind that archangel is a role or a duty performed to relates the Holy God's orders/wills to others (human or angel). In other words, Archangel intercedes between God and others.

Further more, see these text in the following order.

Ezekiel 28:14 - Thou art the anointed cherub that covereth; and I have set thee so: thou wast upon the holy mountain of God; thou hast walked up and down in the midst of the stones of fire.

Isaiah 14:12,13 - How art thou fallen from heaven, O Lucifer, son of the morning! how art thou cut down to the ground, which didst weaken the nations!
For thou hast said in thine heart, I will ascend into heaven, I will exalt my throne above the stars of God: I will sit also upon the mount of the congregation, in the sides of the north:

1 John 3:8 - He that committeth sin is of the devil; for the devil sinneth from the beginning. For this purpose the Son of God was manifested, that he might destroy the works of the devil.

Revelation 12:7 - And there was war in heaven: Michael and his angels fought against the dragon; and the dragon fought and his angels

Revelation 13:8 - And all that dwell upon the earth shall worship him, whose names are not written in the book of life of the Lamb slain from the foundation of the world.

The term "angel" has come to mean a type of creature but the Bible uses the term more as a function describing a messenger. In the Old Testament (Ex. 3:2, 4; Judges 6:12, 14) the "angel" is equated with God.
In Rev. 12:7 Michael is the one who fought the devil. In Dan 12:1 Michael is the one who arises to save his people. These are functions of Jesus. Given the functions of Michael and the fact about angels, then it would be reasonable to assume that Michael and Jesus are the same.

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Armageddon is a Hebrew word describing a place where leaders gather for war in order to gain the whole world.
The war is God verses the evil spirits of Satan--The Battle of the Great Day of God Almighty. The battle happen just before Jesus returns to Earth.
Read Rev. 16:12-19. Some say it's a battle for the human mind, to gain human worship.