I really love Metallica. They have a lot of good songs in my opinion. I'll try to name as many of my favorites as I possibly can...
Master of Puppets
Fade to Black
For Whom The Bell Tolls
The Day That Never Comes
The Unforgiven II
Turn The Page (Original Artisit: Bob Seger)
Nothing Else Matters
All Nightmare Long
No Leaf Clover
Tuesday's Gone (Original Artist: Lynard Skynard)
The Memory Remains
Enter Sandman EDIT: One
Umm... That's all I can think of, at least at this moment.
What are your favorite Metallica songs?
Rob is pretty good on bass as well, as far as I can tell he is able to play Cliff's and Jason's parts without any problems at all.
As far as why so many people like one, its one of their most popular songs. A lot of people who don't care for them love the song just because of how good it is. It also might be because it was in a Guitar Hero game so its one of the few songs they may know.
I personally like the emotion the beginning of the song has. Starting off slow, in despair and turning into rage at the end, I like the build up it has.
Ask someone off the street what their favorite Metallica songs are and you'll probably get a list like this:
2. Sad But True
3. And Nothing Else Matters
4. Enter Sandman