If you're in the UK, download the Winner's Path from Mystery Gift (from Nintendo Wifi) in the next couple of weeks. Beldum can be found at level 5 on this route.
I may be mistaken, but after you beat Red, you will be given a chance to trade a Forretress for a Beldum. Steven will be offering this trade in Silph Company in Saffron City, but first you have to talk to him in the Pewter City Museum.
I don't think you can. I think you have to catch beldum first and then level it up to like lv. 45
Beldum evolves at level 20.
you can catch beldum at route 228 with poke'radar
you must train it to a mettagross and show it to the guy that gave you that beldum.
if you wanna catch beldum it a mass outbreak on route 228
In Saffron City
headbutt a tree,catch a pinceo,evolve it,go 2 silph co.,talk 2 steven and he will trade your fortress for his beldem
You can't catch bastiodon in Pokemon soulsilver.
Pokemon like Anorith, Lileep, Beldum, those kind.
check in the pokedex
Steven Stone will give you a Beldum in exchange for a Forretress.
You get Beldum for free, from Steven after you finish the Pokemon League, go to Stevens house and the ball will be on the table.