Megadeth Drummer Nick Menza: Collapses, Dies at 51

8:40 AM PT -- We're told paramedics tried to resuscitate Nick for 45 minutes ... before transporting him to the hospital where he was pronounced dead.

The former drummer from Megadeth collapsed and died on stage Saturday night.

Nick Menza was performing at the Baked Potato jazz club in Studio City, CA with his band "OHM" when he became lifeless. Paramedics say it looked like a heart attack.

Nick was a drummer for Megadeth between 1989 and 1998

He was 51. RIP.