The opening of Metallica's “Don't Tread on Me” interpolates the melody of “America,” composed by Leonard Bernstein.
“America” comes from Bernstein's musical West Side Story. Metallica used the melody in the introduction to the song, creating a connection between the heavy metal track and one of the best-known works in American musical theater.
The interpolation is a musical quotation rather than a separate cover version of the entire composition. The rest of “Don't Tread on Me” is a Metallica song written by James Hetfield and Lars Ulrich, with lyrics by Hetfield.
The song's title and imagery also connect to the Gadsden flag, whose coiled-snake design appears on the album cover. “Don't Tread on Me” was sent to rock radio after the album's release, but it was not issued as a commercial single.