Fade to Black is a great, classic song. Really shows how metal was moving towards more narrative songwriting. It's like it's right on the brink. There's the loud/soft verse/chorus sort of thing going on in the first half, but even then, the "chorus" part is actually just riffs, no vocals or hooks. Then it builds up to the second half of the song, which goes in a new direction with some great riffs flowing into one another. Riffs will start off one way, then slightly change but still retain their same character, and finally completely morph into something new. You can really feel the influence of Mercyful Fate songs like Evil in regards to Fade to Black's structure.
One is pretty cool, but it doesn't hit me as hard as Fade to Black. This is probably due to the fact that it's the third song that Metallica had written in this style, with Fade to Black and Sanitarium being the first two. I can see why it has become a part of pop culture, since it's probably the catchiest song on the album and there was that video and everything, but it's not really the best cut off of their fourth full-length. I prefer Shortest Straw, Eye of the Beholder, and Dyer's Eve off of that album.
I think that people might latch on to these songs in the early stages of metal appreciation because the whole loud/soft thing makes them seem more sophisticated-sounding to untrained ears, as opposed to something like Slayer where the narrative is a lot more complex but the aesthetic is more uniform. This also explains why (bl)O(w)peth got so popular in the early '00s.