"Immigrant Song" (Led Zeppelin)

That aaah-aaah-aaaaaaaah-aaah! banshee wail.  It's as jarring as it is invigorating.  
Case in point: I was sitting at a New York Rangers hockey game not too long ago.  It was second period, score still 0-0, and the Rangers were struggling to get momentum going.  To be blunt, the crowd was damn bored.  But the moment "Immigrant Song" and Robert Plant's vocal came blasting through the Madison Square Garden speakers during a T.V. timeout, you could feel the crowd perk up.  Not two seconds after puck drop, the crowd began yelling Let's go, Rangers! like their lives depended on it, and the guys on the ice finally woke up to earn their millions.
I bring this up because "Immigrant Song" was made for arenas.  In fact, it opened pretty much every one of Led Zeppelin's shows from 1970-1972.
As Plant notes in this video, the song was inspired by a gig the band played in Reykjavik in 1970.  Zep had been invited to Iceland as British cultural ambassadors and were set to play a concert arranged by the government.  Unfortunately, the band's arrival coincided with a massive strike by the nation's civil servants, so the concert was going to be scrapped.  But one of the universities in Reykjavik (Plant doesn't say which one) stepped in to save the day, calling off classes for two days so that faculty and students could prepare the city's Laugardalsholl Hall, an indoor sports venue, so that the concert could go on.  The warm welcome from the nation and outpouring of affection from these college students really struck the band, Plant in particular.
As he says in the clip, "We got off a plane, and we were given Iceland on a plate."
To capture the feeling of the Icelandic visit, Plant borrowed imagery from the small nation's Viking heritage, imagining Zep as modern day Nordic warriors coming to conquer new lands.
That said, the song is not the cock-rock manifesto for conquering the world that most people think it is; it's meant to be funny.  It's Plant and his pals making a joke about their public image as leaden metalheads.  Actually, quite a bit of Led Zeppelin III is a message to fans and the music press to "lighten up."  (Check out the tracks "Out on the Tiles," "Gallows Pole," and "Hats Off to (Roy) Harper" for further evidence.)