Get ready – Metallica are counting down to something…

What could it be?

Metallica are teasing a new announcement after launching a mysterious online countdown clock.

The metal icons shared a link to MetallicaXX.com on Twitter, which fans click on to be greeted by a countdown timer which is due to hit zero on Thursday at 12noon (GMT).

While there’s no official statement about what it will be, it’s thought that the XX could refer to the number 20 and in turn the 2oth anniversary of Metallica’s landmark S&M album.

After they played a series of S&M2 shows in San Francisco, it’s thought that the announcement could be linked to a DVD release of those gigs.

Fans can likely rule out the prospect of new shows, however, after the band postponed their upcoming tour of Australia and New Zealand due to frontman James Hetfield returning to rehab.

“We are truly sorry to inform our fans and friends that we must postpone our upcoming tour of Australia and New Zealand,” Lars Ulrich, Kirk Hammett, and Rob Trujillo said in a statement. “As most of you probably know, our brother James has been struggling with addiction on and off for many years. He has now, unfortunately, had to re-enter a treatment program to work on his recovery again.”

Hetfield’s addiction and alcoholism issues were detailed in the 2004 documentary Some Kind of Monster; after the film’s release, the singer checked into a rehab facility.