A little background, Archangel started as simply Angel, a mutant from a high-ranking family who used his abilities to help people and had a thing for Jean Gray. He was part of the X-Men for a bit, and through a series of events (go read it, guys), developed gangrene in his wings and was deformed. After an attempt on his life, he is rescued by Apocalypse. Of course, right? Apoc offers him the restoration of his wings if he will become a horseman. The genetic modifications that Apoc performs on Angel give us the Archangel that most are familiar with: Blue skin and metal wings with feather projectiles. Angel becomes Death, and is placed as leader of the horsemen.
Anyway, he’s Death for a while, and does some rather bloody and brutal things to some people – some who deserved it and some who didn’t (seriously, go read it). He settles on the name Archangel after deciding to rejoin X-Factor, the team that consisted of the original X-Men who’d left after Professor X put Magneto in charge as leader.
Okay, so take all of that, plus these photos for visuals: