At this point in history everyone has heard every Led Zeppelin song at least four hundred times. If not, you've got some catching up to do, so put down that Mars Volta record and get yourself the Complete Led Zeppelin and we'll talk in the morning.
I picked the five moments that if I had to explain Led Zeppelin to someone from outer space or Utah I would use as my starting points (just kidding, we love you, Utah!). You might choose something different. In fact, I'd count on it.
The Orgasm Suite on "Whole Lotta Love": When I first heard these moans in the middle of the song when I was a wee lad I assumed something was wrong with my stereo. Why was this happening? It seemed so unusual. It sounded like noises far beyond, say, "Yellow Submarine." I was sure there were laws against this sort of thing. There might be.
The Instrumental Build of "Stairway to Heaven":Yes, everyone's heard this song a million times. That still doesn't mean you can't be impressed with how Jimmy Page layered the guitars and made the song sound like an ascending piece of music that could in fact be walking up a literal "stairway" until you get to the top. Give the guy props for being conceptual.
The Opening Drum Shot of "When the Levee Breaks": Granted, everytime I hear the opening drum shot I think I'm about to be listening to the Beastie Boys' Licensed to Ill album, since they sampled the drum beat for their own "Rhymin' & Stealin'." And it's easy to hear why. John Bonham isn't just hitting the drums, he seems to be dismantling them. Then the harmonica kicks in and suddenly the levee breaks. Freaky.
John Paul Jones' Mellotron on "No Quarter": John Paul Jones was always the quiet member of the group, the one who seemed to leave the crotch-stuffing to others. He played all the pretty instruments in the group and always seemed to be sent to the back of the stage for his efforts. But his work on "No Quarter" will NOT BE DENIED. He gets on that spooky sounding mellotron or whatever keyboard he hooked up and he drops the temperature in the room by at least 50 degrees until you can hear the wind whipping and the snow crunching under your feet. Why does man live in such uncomfortable climes?
The Flubbed Note on the Solo to "All My Love": This is where I show off my true jerkitude. For all their great musical alchemy, Led Zep still managed to leave some of their mistakes on the record. Better attuned listeners than myself can name off plenty of spots where Page flubs a riff or note, but for a thick-head like myself it takes something really obvious to set off the alarm bell. Nowhere is that more noted than in the solo to "All My Love" where just as the keyboard-trumpet solo is about to end TWO notes clink together where obviously only one should broadcast. Love it. Even rock gods aren't perfect.