Which Metallica song contains an introduction interpolating Leonard Bernstein's “America”?

“Don't Tread on Me” contains an introduction interpolating Leonard Bernstein's “America.”

Bernstein composed “America” for the musical West Side Story, which premiered on Broadway in 1957. Metallica's song uses the recognizable melodic idea in its opening, creating an unusual connection between a heavy-metal album and a celebrated American musical.

“Don't Tread on Me” takes its title from the motto associated with the Gadsden flag. The flag's imagery also influenced the coiled snake on the Black Album cover. The song therefore connects the album's visual identity with an explicitly American symbol.

Although it was sent to rock radio shortly after the album's release, “Don't Tread on Me” was not issued as a commercial single. The five official singles from the album were “Enter Sandman,” “The Unforgiven,” “Nothing Else Matters,” “Wherever I May Roam,” and “Sad but True.”