Metallica’s Robert Trujillo Celebrated Birthday by Jamming With Post Malone + Andrew Watt

Metallica bassist Robert Trujillo turned 56 last week (Oct. 23), and it appears the musician celebrated by joining a jam session with rapper Post Malone and music producer Andrew Watt.

That's what one could guess based on the photos that have since turned up on Watt's Instagram page. The producer and close Posty associate — who recently worked on Ozzy Osbourne's Ordinary Man album — shared plenty of images of the joint birthday jam sesh. Watt celebrated his 30th on Oct. 20.

See some of the pictures down toward the bottom of this post.

"DIRTY 30," the producer said of one photo of himself standing amid Trujillo and Posty, all three wielding an instrument and putting on their best rock faces. Watt called it the "best jam of all time."

The producer tagged Red Hot Chili Peppers' Chad Smith and Foo Fighters' Taylor Hawkins in the same photo message, giving credence to the idea that both drummers also took part in the birthday jam among musicians. In a follow-up photo set from Watt, an image of Hawkins does indeed appear.

But, of course, what would a birthday be without some cake? In the same subsequent set of photos, one shot shows Watt and Trujillo smiling as they each hold a birthday cake portraying their respective likenesses.

But maybe the musicians were cookin' up something else besides just birthday cake? Perhaps a Watt-produced collaboration between Posty and Trujillo (and Smith or Hawkins) is in the making.

Either way, it sure looks like one hell of a birthday jam!