METALLICA has played "Enter Sandman" so many times, they can play it backwards. Maybe.
In a clip that was reportedly filmed in 2013, the guys are jamming in the studio when they try to play the song backwards by playing the notes in reverse order. JAMES HETFIELD even tries to sing a line backwards.
The video is then played in reverse to see if it actually sounds like "Enter Sandman". . . and it kind of does.