Depending on how fast the song is, it can be a very complicated melody or a very simple one.
There are no rules in art. Do what feels right to you. Most people take inspiration from other artists they admire, so you may listen to some of your favorites and see how they do things.
But in the end, the choice is yours.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.