Metta World Peace has a few suggestions on how to prevent nuclear war with North Korea ... and it doesn't involve bragging about the size of your button.

Truth is ... Metta thinks his old pal, Dennis Rodman, may have been on to something when he went over to Pyongyang a few years ago.

"He tried to do the right thing, he just ... it turned out bad," Metta says ... "but his heart was in the right place."

Metta says he's not looking to be a politician -- he just doesn't want anybody to get bombed.

True that.