So this is a cool story:
Apparently James Hetfield (disguised) got in the snakepit for Mastodon’s set at Rock in Rio. A guy on a Metallica forum was at the show and said he realised it was James after a few songs.
He also said that the dude in the picture in the mask had a security guy constantly watching him and then help him out of the pit. Then someone asked the security guy if it was James and he said he was.
You gotta love Papa Het

