Led Zeppelin are so good they can make you think the main riff in this song is an odd time signature. But count it: Four. Beats.
What locked-in funky rock this is. The guitar is just buzzy enough, grinding out compressed chords. The really awesomely phrased guitar solo shows us a rare test of the wah pedal by Jimmy Page. The groovy John Paul Jones bass line calls back to the fun of Led Zeppelin II, four albums prior. I'm thinking especially of the bass line in "Lemon Song," another song about food that just doesn't seem to be about food.
The drums could've played it straight on the verses and the song would never have made it out of the writing stages, much less to opening track status on the titanic Physical Graffiti album. Instead, the drums simultaneously finesse around the beat and crack with John Bonham's unsuppressable ferocity. The drums doubling the guitar rhythm on the chorus leads to cool hanging notes where there may have been only standard rock-pattern drum thudding had someone less bombastic held the sticks. The cardinal rule: Drum creativity is song creativity.
For vocals, I really think the whole Physical Graffiti album is Robert Plant's masterpiece. There is so much fluidity here, such an organic delivery, almost like he's just making up the melody on the spot. However, the melodies repeat pretty faithfully, demonstrating how crafted they are.
The ending has the best little repeat singing part, not to mention a harmonica solo right when we really needed a harmonica solo in our lives. It's up there with "When the Levee Breaks" for Plant's harmonica work, which is weirdly underrated. He's no Paul Butterfield, but come on, he's a legitimate instrumental contributor.
Led Zeppelin have this reputation as being this dark band, I think mainly due to Jimmy Page's purported fascination with the occult. But they were really one of the great light bands to ever play, with so many songs like this one, full with fun and celebration.