Sometimes Robert Plant was a sex-sick horndog, singing about pleasuring his lady with "every inch of (his) love" or reflecting on the joys of lemon-squeezing. Other times, he was a Tolkien-quoting mystic, coughing up epic-fantasy lines like, "The mighty arms of Atlas hold the heavens from the Earth."

That same fascinating split-personality applies to Led Zeppelin as a whole. Rock's mightiest quartet could lay down a deep psychedelic blues like no other band on the planet, but when they stretched out into headier, artsier territory, they were just as deadly.

'Achilles' Last Stand,' the ten-minute opener from 1976's guitar-dominated 'Presence,' is one of Zeppelin's most visceral (and most underrated) anthems and No. 22 on our list of the Top 50 Led Zeppelin Songs. A longtime Jimmy Page favorite and a staple of the band's late-'70s live set, 'Achilles' was originally written after Plant suffered a debilitating ankle injury after a car crash in Greece; confined to a wheelchair, the singer was visited by Page for a month-long writing session, out of which this majestic track arose.

Though Plant often complains in retrospect of his pained, unexpressive singing, it remains one of his most passionate vocal deliveries; underneath, John Paul Jones (using a custom eight-string bass) and John Bonham provide chugging, relentless rhythms, while Page layers up a virtual orchestra of electric guitar leads--all the more impressive considering he did all the overdubs in one marathon all-nighter.