The intro to Metallica's "Don't Tread on Me" uses a phrase from "America," a song from West Side Story.
The instrumental introduction incorporates an eight-bar phrase from Leonard Bernstein's musical. Metallica adapted the recognizable melody as part of the track's opening, creating a connection between the band's American-themed lyrics and a famous piece of musical theater.
"Don't Tread on Me" appears on Metallica's 1991 self-titled album and was issued as a promotional single on August 29, 1991. Its title references the Gadsden flag and its coiled-snake motto, imagery that also relates to the snake shown on The Black Album's cover.
The song was never released as a commercial single, which is why it is sometimes incorrectly counted among the album's five official singles. Metallica did not perform it live until the European leg of the 2012 tour celebrating the album's twentieth anniversary.