I think you're referring to Titanium Man, the guy that looks like a cheap super villain knockoff of iron man (black metal with green lights).


He will try to destroy the nuclear containers when he's not firing at you. The strategy here is relatively simple though; get his attention by firing repuslors at him when he's shielded. This will keep him attacking you more often than the containers in the room. Eventually he will discharge a lot of radioactive energy, so stand back. Once he expend the energy, his shield is drained and he's vulnerable for a few second. Get close as fast s you can, and punch him before his shield goes back up.

If and when he runs toward a container and starts destroying it, he's again vulnerable, so punch the crap out of him some more. He's vulnerable also, after he fires a volley of radioactive blasts at you, so try to close the distance to counter attack before his shield goes back up.

The key is punching, your other weapons aren't too useful here, and the unibeam takes too long to charge.

(Actually, melee combat works with all of the game bosses)