'AGT' Metal Grandpa : I'm With The Band Now!

John Hetlinger made it to the big time -- and it only took 82 years!

Hetlinger -- who went crazy viral for rocking out to Drowning Pool's "Bodies" on "America's Got Talent" -- will join the band onstage Friday in front of thousands at Chicago Open Air music festival.

Like a true rock star -- priority #1 is partying. The band says it's treating John to all the alcohol he wants.

Hetlinger will join Drowning Pool at their signing booth after their set -- here's hoping he gets to autograph someone's boobs.