He can play Smoke on the water (who doesn't?), almost the Crazy train intro, the Sweet child o' mine intro and the first two parts of Fallen leaves, but it could have sounded better. Which songs do you think he can learn pretty quick? Btw, he learned the Holiday intro in something like 20 minutes.

Iron Man
Smells like teen spirit
Enter sandman
Breaking the law

just a few to start out with


if he is having problems fretting, he should practice that first before trying to learn any song, chords are the best way
Almost any Nirvana stuff. Green day stuff is generally pretty easy too. Just as long as he can rip off a good powerchord, it's all good.