heracross learns close combat at lv.37
if palkia has low helth then yah because palkia is like all the other Pokemon but there is only one of palkia so try not to faint palkia
you cant find it anywhere, it's not a TM it's a specific fighting move
you just evolve your staravia and it will say that starptor wants to learn close combat
in platinum version you beat 1st gym leader