Metallica Now Magnetica?
Blabbermouth speculates that this just might be the artwork to their new album "Silence The Critics, Even The Ones That Praise Us" (not really the title), which is expected to street in September.
The mysterious artwork features two back to back magnets shooting out the M in Metallica's logo. It was posted on the Metallica website under the headline "???". Our guess is that it was sent in by a fan and they liked it enough to post it, but it could be the artwork (if they have $50 budget for such things). - Check it out here