it is about the vikings. take, for example, one verse,"To fight the horde, singing and crying: Valhalla, I am coming!". Valhalla is, in norse mythology, the "Hall of the Slain", presided over by Odin, father of the gods. the lyrics of the song also refers to the "midnight sun", where everything north of the Arctic Circle shines day and night for part of the summer. the "midnight sun" can be seen in parts of Norway, Sweden,and, i believe, Iceland, all scandinavian countries.