John Mayer the GI?

Breaking up with Jennifer Aniston has brought out John Mayer’s macho side!

The crooner recently spent the day with Marines at Air Station New River and Camp Lejeune in Jacksonville, N.C.

“Believe me when I say that the day was life-changing,” John said of his visit to the base, which included shooting a machine gun, sparring with marines trained in the martial art of Krav Maga and visiting wounded Iraq veterans.

“It was an awesome day,” Staff Sgt. Angela Mink tells OK!. “I think John would make a good marine — but I wouldn’t want him to give up the blues guitar!”

We agree, stick to the music, John!