Sleep with one eye open, gripping your xylophone tight.
Metallica traded their amps, scowls and moody body language for classroom instruments when they delivered an unthinkable performance on The Tonight Show Starring Jimmy Fallon.
The Hall of Fame-inducted heavy rockers teamed up with the late night host and the Roots for a never-to-be-seen-again rendition of their 1991 classic "Enter Sandman," from the band's eponymously titled fifth album.
Just for one night, James Hetfield took on the toy clarinet, Lars Ulrich beat a Fisher Price drum, Kirk Hammett got to work on a melodica and Robert Trujillo tackled the baby electric axe.
The metal four-piece are back in business with a new album, Hardwired…To Self-Destruct, due out Friday (Nov. 18). There won't be any classroom instruments played on it.