There are only five references to Michael the Archangel in the Bible, all of which clearly show that he and Jesus are not the same being. The name Michael, which is of Hebrew origin, means "who is like God" and is Strong's Concordance #4317 for its use in the Old Testament and Strong's #3413 for its use in the New Testament.
The first mention of Michael the Archangel is in the book of Daniel, Chapter 10, where we are told of a discussion between the prophet and a "glorious man" regarding prophecies of Persia and Greece.
A Special Guest
Daniel, before he records his discussion that mentions this spirit, states that he had been fasting and praying to God for three straight weeks (Daniel 10:2 - 3). He then saw a vision of a man, which only he witnessed, that frightened him to the point that it sapped all his strength (Daniel 10:5 - 8). Verse 12 then relates that the "man" came because the prophet's words had reached God in his heavenly throne. The "man," who was likely Gabriel the Archangel, then mentioned Michael.
But the prince of the kingdom of Persia withstood me one and twenty days: but, lo, Michael, one of the chief princes, came to help me; and I remained there with the kings of Persia (Daniel 10:13, KJV).
Michael is referred to as a "chief prince" or one who is first in rank or power. He was (and is) a very powerful and influential spirit being. Continuing in Daniel 10, note that he is again mentioned in verse 21 where he is called "your prince."
"But I will shew thee that which is noted in the scripture of truth: and [there is] none that holdeth with me in these things, but Michael your prince" (Daniel 10:21, KJV)
Moving on to Daniel 12:1 the following is stated.
At that time Michael shall stand up, the great prince who stands watch over the sons of your people: and there shall be a time of trouble, such as never was since there was a nation, even to that time. And at that time your people shall be delivered, every one who is found written in the book (Daniel 12:1, NKJV).
It should be noted that righteous spirit in question has yet to stand up and defend Daniel's people, the Israelites. The next mention of this spirit being is in the New Testament book of Jude where verse 9 reads as follows.
Yet Michael the archangel, in contending with the devil, when he disputed about the body of Moses, dared not bring against him a reviling accusation, but said, "The Lord rebuke you!" (Jude 9, NKJV).
Jude 9 cannot be referring to Jesus since, as a member of the Godhead, he would have no need to call upon a higher power in order to rebuke Satan. It is also interesting to note that here this spirit is called an archangel, which, according to Strong's Concordance #743, means a chief angel.
A Final Mention
The last mention of this angel in the Bible is the book of Revelation.
And war broke out in heaven: Michael (not Jesus!) and his angels fought with the dragon; and the dragon and his angels fought, but they did not prevail, nor was a place found for them in heaven any longer (Revelation 12:7 - 8, NKJV).
This incident is identical to that of Daniel 12:1 and is still future and does not conflict with Luke 10:18 where Jesus said, "I saw Satan fall like lightning from heaven." Satan is a spirit being who will ultimately be tossed out of heaven twice. So we have seen that Michael the Archangel is a powerful spirit being and prince whom God has designated as protector of Israel. He is not, in spite of what many commentaries state, a manifestation of Christ before his human birth.