"The Unforgiven" is a single from Metallica's 1991, self-titled album, Metallica. Though one of the slower tracks on the album, its chord progression is distinctly one of the heavier. The song describes a man who never took risks and ultimately regretted it.
Drummer Lars Ulrich explained that the band wanted to try something new with the idea of a ballad - instead of the standard melodic verse and heavy chorus (as evidenced on their previous ballads "Fade to Black," "Welcome Home (Sanitarium)," and "One"), the band opted to reverse the dynamic, with heavy, distorted verses and a softer, melodic chorus, played with classical guitars.

The horn intro was essentially taken from a Western movie and then reversed so its source would be hidden, as Hetfield later explained on Classic Albums: Metallica - Metallica. While Metallica has never disclosed what movie the horn was taken from, it is believed to be from a piece of music called "The Showdown," which was composed by Ennio Morricone for the 1965 Clint Eastwood "Spaghetti Western" film, For a Few Dollars More.