There are a number of things you can do with Metagross-
Iron Defense-While not used as much due to most people exposing his lower special defense, this move makes him almost invincible with respect to physical moves, works well with leftovers too.
Explosion- A good last ditch move for when he's low on health or you desperately need to get rid of a pokemon on your opponent's team.
You could go for a different approach, by replacing meteor mash and agility with hammer arm and gyro ball. Hammer arm would lower your speed, thus boosting the power of gyro ball.
Zen headbutt-a good psychic move if you need some STAB power.
There are a ton of things you can do with him.