Metallica's “The Unforgiven” eventually received two sequels.
The follow-ups were “The Unforgiven II,” released on the 1997 album Reload, and “The Unforgiven III,” released on the 2008 album Death Magnetic. Together, the three songs form a recurring series in Metallica's catalog.
The original “The Unforgiven” appeared on the 1991 self-titled album, commonly called The Black Album. It was released as that album's second single after “Enter Sandman.” The song's lyrics focus on an individual's struggle against forces attempting to control or subjugate him.
The numbered titles are easy to confuse with unrelated Metallica songs because the band has used recurring themes and titles elsewhere. In this case, however, the sequence is explicit: the original is followed by Part II and Part III. The later songs are not alternate versions of the Black Album recording; they are separate compositions released on later studio albums.