No ideas, but I saw the thread title and thought it was about looking at Facebook on a Palm, which would be substantially less interesting a topic...
No suggestions, (don't know the tunes, never really got the Metallica bug (but my son sure did, so I know the basic vibe, but that's about it) but one of my "stock" approaches to challenges like this is to deconstruct the melody & then set about putting it back together with different phrase displacements, etc. If it's no longer immediately recognizable, so much the better - sometimes. Then, once you have a melody that is divorced from the original context, you can treat it as something "original" and go from there. Then, if you want to make it more recognizable, you can tweak it back as much or as little as you want/need to. Depends on where you want to go, who you want to go there with, and why you're going there in the first place.
That's one way to do it, just one. Take it for waht it's worth, and hopefully you'll find your own way, all the way. Good luck!