As has been mentioned the song tales the story of the battle between Frej and surtur.
I do not however think the moral of the story is to always fight no matter the odds. To me the "fate of frej" perfectly represents part of the Norse belief one of the few things that is predetermined is your death and frej goes into the battle knowing for sure he is going to perish for such has been foretold.
However he will fulfill his fate even if it is in vain.
This also explains, atleast partly, why Frej was such a revered deity, this and the fact that he was also a god of fertility
As has been mentioned the song tales the story of the battle between Frej and surtur. I do not however think the moral of the story is to always fight no matter the odds. To me the "fate of frej" perfectly represents part of the Norse belief one of the few things that is predetermined is your death and frej goes into the battle knowing for sure he is going to perish for such has been foretold. However he will fulfill his fate even if it is in vain. This also explains, atleast partly, why Frej was such a revered deity, this and the fact that he was also a god of fertility