Mech was actually surprised that the robot did not know about Halo, then again when he thought about it, the guy is a robot, a sentient one as far as he could tell, wherever he is from he was either sheltered or build after the games came out.
"Dude, the Halo games are possibly the best shooter games you could find, come I'll teach you all you need to know"
With that Mech guided his new "best friend" to the living room and started up the game, giving David a remote and teaching him the game