The opening of Metallica's “Don't Tread on Me” interpolates “America,” composed by Leonard Bernstein for West Side Story.
The brief musical reference appears before the song's main riff and is one of the album's more unusual arrangement details. It connects Metallica's heavy-metal track to Bernstein's famous 1957 musical score, creating a recognizable contrast between orchestral theater music and hard rock.
“America” was written by Leonard Bernstein, with lyrics by Stephen Sondheim for the original stage musical. The song is associated with a debate about life in the United States and is one of West Side Story's best-known numbers.
The reference is sometimes described loosely as a sample or cover, but “interpolation” is more precise here: Metallica uses part of the melody within a new composition rather than presenting the complete original song. “Don't Tread on Me” appears as the album's seventh track.