Hey man whats up. The "openings" are actually called intro's just to clear up any confusion, what everyone ese calls em just so were on the same page. But judging by the stuff you already learned, you can learn Iron Man by Sabbath, very easy, but learn it as power chords and not on the E string tab here: http://www.ultimate-guitar.com/tabs/b/black_sabbath/iron_man_ver4_tab.htm . Also Paranoid is pretty simple. Last but not least Metallica has some very easy riffs for beginners. Seek and destroy is a great beginner song as its easy and gets all your fingers goin. Enter Sandman, Whever I may Roam has a killer intro, and off their new record, Suicide and Redemption is very easy. Check em out and get back to me I'll shoot you some more or let me kno what you need help with.

Also, don't just learn the easy verions of songs like on a lot of Youtube videos, learn the actual notes through tabs and songbooks. If you can't jam along well to cd's, your either out of tune or your playing the simplfied version of the song.