Depends on the version you're playing. Considering you're playing
ruby, sapphire and emerald(cos its under that catergory), metagross should learn
meteor MASH at level 55.
on level 53
It will lern metormash at level 53 meteor mash*
In Pokemon Pearl, Diamond, HeartGold, and SoulSilver, Metagross can learn Stealth Rock by using TM76 on it.Since TM76 is no longer Stealth Rock in Black and White, if you want a Metagross that knows it in those games, you must use the TM in one of the earlier games and trade it to Black or White.
To get Metagross, make sure you have a Beldum. Then raise it so it can evolve into Metang. Then evolve it at level 45 but I rather make it evolve at level 50 because Metang can learn the move Meteor Mash then let it evolve into Metagross.
meteor mash
level 595,584,395,492,000 Don't give bad answers like that. It's level 55.
Yes, you can have a level 50 Metagross with Meteor Mash. you have to trade it to your Pokemon Diamond/Pearl/Platinum through Pal Park. Pal Park opens up after you receive the National Pokedex. (On your DS game...) It learns Meteor mash at level 55. However you can still make a metang not evolve (by pressing b during evolution or giving it an everstone.) and make it learn Meteor mash at level 50 and only let it evolve at 50 (it usually evolves at lv.40)and then you will have a metagross with Meteor mash at level 50.
Metagross can only learn Earthquake with the use of a TM.
No.
get beldum from steven and evolve it into metagross and train it until it lerns the move
Metagross learns Hammer Arm on level 45.
Well, Metagross can learn all sorts of moves. I will tell you some of the TMs and HMs he/she can learn, and also some of the moves Metagross learns while he/she is leveling up. As Metagross levels up, he/she can learn[sorry,but these are not in order] Bullet punch, Psychic, Zen headbutt,Magnet rise,Take down, Confusion,Meteor mash and so on. In HMs and TMs, Metagross can learn Hyper beam,Psychic,Flash cannnon,Thunder[but I'm not positive about Thunder.],Earthquake,Secret power,Double team,Rock tomb,Shadow ball,Protect,Reflect,Sludge bomb,Cut,Rest,Flash,Return,Rock smash and Strength. There is many more moves, so I would suggest you go to Serebii.net Pokedex for all the moves. Hope this helped.