What’s this? Dave Grohl just wrote to Metallica? That’s right, former Nirvana drummer and current Foo Fighters frontman Dave Grohl has released an “open letter” to Metallica. Call me an idiot, but there’s only one reason he’d do this – he’s afraid it’s going to suck. OK, maybe suck is a harsh word… he’s afraid the album they’re going to release will not rise to it’s potential (aren’t we all?). Anyway, great letter, and I…