Songs are short and quite hard to analyse. On the other hand they're easy to find and apply random meaning to. I would say that markers may look negatively on songs unless you have a very convincing argument.
Some techniques you may like to look at are:
lyrics - who, what, context
tone
rhythm/meter
rhyme or lack of
key
modulation and effect on tone
analyse it in parts - structure of song overall and structure of each verse/chorus
etc etc.