i think you have to just level him up untill he learns it i may be wrong though.
oh wait i figured out that hes does not learn it
Its a TM
Sometimes u can breed a pokemon that knows thunderbolt with magneton and u will have the pokemon and at the daycare center make sure u keep a eye on it so u dont have 2 eggs o and if u need more help come to Kankuro's Pokemon Board ill give out locations of pokemon and items and unlockables