Ahh good ol' R/S forum, you haven't changed much have you?
Ahem, for the moveset, it looks okay, should get you by in-game no problem. If this is a serious battling pokemon you might want to have Earthquake over Metal Claw, as you really only need one steel type move, and Meteor Mahs is enough. If you don't want to waste the TM or you've already spent it, give it Return, a nice solid physical attack with great PP and accuracy. (You can get Return by showing the TM man in Pacifidlog a pokemon that really likes you. I believe his is the house on the far right, and it has two Marill in it. He'll only give out one TM a week so if you visited him before you'll have to check and he'll tell you what day he'll be giving out TMs.)
Oh, and if you give Metagross Return you'll have no need of Hyper Beam (STABEd Meteor Mash is about as strong, and it doesn't cost you the regrouping turn,) So I say either teach it a defensive move, i.e. Iron Defense (Move Tutor, you have to give him a Heart Scale) or maybe Amnesia. (Same as Iron Defense.)
Oh, and the Steel empowering item is called the Metal Coat, and I'm not sure where you get it in R/S but I know you can steal them off of Magnemite w/ a Pokemon that knows Thief/Covet. It can take a while tho, I would recomend giving it either the Shell Bell or Leftovers, both are health recovering items and quite handy.
So, maybe this set:
Metagross
@ Leftovers or Shell Bell
Psychic
Earthquake/Return
Meteor Mash
Iron Defense/Amnesia
It's up to you, maybe try out different ones and see what works best, that's one way you'll find out for sure.![]()