Mastodon Hushed and Grim photo: thegroovemanscollection There’s a reason why Mastodon is currently one of the biggest metal bands that still matters. They don’t pack in stadiums, I know, but they’re not playing tiny venues either. They’re big enough to play all the late night shows (I’ve seen them on Letterman, Kimmel, and Fallon), and even occasionally do the oddball appearance (remember when they were on the Human Giant show?). Also, they have a sense of humor about themselves. These...