The intro to “Don't Tread on Me” on Metallica's 1991 album interpolates the melody of “America” from West Side Story.
Leonard Bernstein composed the music for West Side Story, the stage musical created with lyrics by Stephen Sondheim and a book by Arthur Laurents. Metallica used the recognizable melodic idea in the song's opening before moving into its own heavy-metal arrangement.
“Don't Tread on Me” takes its title from the motto associated with the Gadsden flag, which also appears symbolically in The Black Album's cover design through the coiled snake. The song itself was promoted to rock radio but was not released as one of the album's five commercial singles.
The musical connection is sometimes overlooked because the rest of the track is firmly rooted in Metallica's sound. The reference is an interpolation rather than a full cover of “America,” so the song remains an original Metallica composition.