The band performing in the beginning of the film is Mushroomhead. The score to the movie was performed by Midnight Syndicate and is available for purchase ("The Rage: Original Motion Picture Soundtrack").
Nowadays it's a common method to release both the R-rated version and the Unrated version simultaneously. Therefore it's not a big surprise that there are two different versions of The Rage available on DVD. As you can imagine for a horror movie the Unrated version features several new gory scenes that are missing in the rated version.
A crazed scientist experiments with a rage virus on innocent victims in a laboratory in the woods. When his monstrous subjects escape and vultures devour their remains, they became mutations seeking to feed on humans.
