Who do mainline Protestants believe an "archangel" (such as Michael) to be?

Some sects including Jehovah's Witnesses believe the archangel Michael to be one in the same with Christ . The basic premise of this claim seems to stem from the unique usage of the role archangel rather than just any-ol-angel. > Michael is the only one said to be the 'archangel', meaning 'chief angel' or 'principal angel'. I would like to know what a mainline Protestant understanding about the role of "archangel" is. What makes them different from a mainline* angel? Do they bear any special relation to Christ? How many might there be? Also, are there any ways in which Protestants view the type "archangel" differently than other major traditions? \* Sorry, couldn't resist.