The intro to Metallica's 1991 song “Don't Tread on Me” interpolates “America,” composed by Leonard Bernstein for the musical West Side Story.
The brief melodic quotation appears at the beginning of the track before the song settles into its heavy-metal arrangement. Metallica used the recognizable passage as a musical reference rather than presenting the full composition.
“America” is a song from West Side Story, whose music was written by Bernstein. The musical premiered on Broadway in 1957 and became one of the best-known works associated with his career.
The song title “Don't Tread on Me” also connects to the album's visual design: its cover includes a coiled snake derived from the Gadsden flag, whose motto is the same phrase. That visual link is separate from the Bernstein interpolation.