I suggest using the masterball.
No,
no you can catch it. However you can trade Pokemon to get geodude and metagross on black and white!
Yes you can always go back and fight nascour again in realagam tower and get metagross.
In the giant chasm, you can catch them. however, i would recommend catching a metang instead, because metagross are extremely rare.
at the giant hall in the swirling grass
After beating the Elite Four, head to Steven's house in Mossdeep. In there, take the pokeball. The Pokeball will give you Beldum, which you will have to level up to Metagross.
Catch it from some rooms in indigo, as a beldum, train it, and it will slowly evolve...
Beat Evice With Pokemon Over 60's or you can beat evice with metagross lvl 70 metagross save metagross for machamp because metagross know's psychic or espeon lvl 70 because machamp know's earthquake and catch tyranitar with a master ball i think he is lvl 55
You cant, but you can catch it's pre-evolution: Beldum, in the Safari Zone.
If you mean metagross, you beat the Pokemon league and return to steven's house in mossdeep city. there will be a pokeball on the table. it contains Beldum, and you have to train it to lvl 45. You will get the metagross.
You can just get him from the same place , the only Pokemon that does do that is Metagross , and tyrannatar , the hardest two to catch in the game.
Yes, it is worth the catch. Beldum = Metang = Metagross = awesome. But it is almost impossible to catch and if you do want one than it is near the battle frontier and the other one above it.