Attack on Titan is a pretty great series, and one of the best things about it is that it's got great music.
But if you've watched it, you know that already, right?
So if you haven't, or even if you have, here's a "metal" cover of the OST song "XL-TT," which stands for "extra-large titan." ...No, I'm not sure why they chose that particular idiosyncratic naming scheme.
Whatever, it's still amazing.