Hey,
I just wanted to say that the banlist shown on Smogon right now was for last generation. This generation's banlists aren't up on the site yet, though you can find them on the forums. Garchomp isn't Uber in the fifth generation. :3
Metagross's speed isn't useful enough to be Scarf'd, though you can certainly try Choice Band Bullet Punch and see how that works for ya.