Well, Anchyyy recommended great bands!
But, if you want to narrow it down a bit... if you like Metallica, I'd say.......
MUCC. I'm currently saturated with their music... I love it. It's just so............. GOOD!!!!
I would also COMMAND you to listen to D'espairsRay and Dir en grey, too. They are both EXCELLENT bands (please excuse me the caps... it's just... I needed to say those things LOUDLY :sorry: ). For Dir en grey, grab a bunch of songs from a few different albums, because their music is so diverse you can't always get an impression of it straightaway. (For heavy stuff, get their song Pink Killer! It's music to die to!
)
If you have the chance, also you should really check out Gazette (particularly the Disorder album), Rentrer en Soi (personally I think Sphire-Croid is their best album), Galneryus, Aushvitz (those last 2 for real top guitaring!).......... hell, I wanted to "narrow down" the recommendations and here I am blethering on!
One last thing (last, I promise!). Two bands you should definitely check out if you can are Deathgaze (only they haven't released much yet, only a couple of singles, but they are very good!) and The Zolge (Deadly Sanctuary album) (but The Zolge are now disbanded...)
I hope that helps! And, I hope you go for it and DO listen to these - they rock!