Immigrant Song / Hey, Hey, What Can I Do

Written during the band's cultural exchange tour of Iceland, 'Immigrant Song' famously channels Viking mythology and Nordic conquests over a blistering, galloping John Paul Jones bassline. Robert Plant's iconic, wordless battle cry in the introduction became one of heavy metal's most recognizable vocal hooks. The acoustic B-side remains a celebrated rarity, as it is the only non-album track the band ever officially released during their original tenure.