Revelation 12:7 (ESV)

7 Now war arose in heaven, Michael and his angels fighting against the dragon. And the dragon and his angels fought back,

The name Michael is a composite of three Hebrew words that literally mean, who like God. So the bearer of the name is a living confession of the incomparability of the Lord. In this instance, the bearer of the name is an angel—or better, a captain of angels (note the words his angels). Earlier Scripture had introduced the reader to Michael when he was described as the great prince who has charge of your people (Daniel 12:1; Daniel 10:21). From Daniel’s words it appears that nations have their own angelic force engaged in spiritual battles for the benefit of their (assigned?) nation (Daniel 10:13, Daniel 10:20). Too little, however, has been revealed in Scripture on this point for us to be definitive on it. What is clear is that Michael is a leading angel charged with the wellbeing and protection of the people of Israel (the church of the OT; as of Jesus’ ascension, the church of the NT). In the present passage we are told that Michael and his angels were entangled in heavenly battle against the dragon and his angels.