Metallica's “Don't Tread on Me” interpolates the introduction of “America” from West Side Story.
The Black Album song begins with an eight-bar phrase from “America,” the well-known musical number associated with Leonard Bernstein's music and Stephen Sondheim's lyrics. Metallica uses the phrase as an instrumental introduction before moving into its own heavy-metal arrangement.
The connection is meaningful because “Don't Tread on Me” draws on American Revolutionary imagery and the Gadsden flag. The song's title is the flag's motto, and the album cover includes a snake based on that same design. The borrowed musical phrase adds another specifically American reference.
This is often described as a sample, but “interpolate” is the more precise term for the musical quotation in the song. “America” is also easy to confuse with other West Side Story titles, such as “Maria” or “Tonight,” neither of which supplies the Black Album introduction.