The opening of “Don’t Tread on Me” on Metallica’s 1991 album interpolates music from West Side Story.
The album’s track notes identify the intro as an interpolation of “America,” a piece composed by Leonard Bernstein for the musical West Side Story. The brief reference appears before the song’s main heavy-metal material, creating a musical connection between a famous Broadway score and Metallica’s hard-edged arrangement.
An interpolation means that a musical passage is incorporated into a new composition or performance. It is not necessarily the same as a direct sample of an existing recording. This distinction matters because “Don’t Tread on Me” uses the melody in its own recording rather than simply inserting a piece of the original West Side Story soundtrack.
“Don’t Tread on Me” was included on the album but was not one of its five commercial singles. It was sent to rock radio, which sometimes leads listeners to treat it as a single. The track is number six in the album sequence and has a listed length of four minutes.