Personally I find the easiest way to come up with lyrics is to dig into the experiences or aspirations that are prominent because of the underlying feeling of them. If you have angst or a strong yearning for something/someone, good times/bad times, or an imagined but very much sought after life experience you have knowledge of, all of these elements are at your disposal. You might have to put a little shyness at unwrapping aspects of yourself to one side and maybe manipulate some things in how you write them, if you really don't want to share in an obvious way something which is deeply personal. Authenticity tends to come across much better than bullshit, especially if it's something that's touched a raw nerve. I don't see genre as a barrier for any subject, though I appreciate it needs to be deliverable in a way which suits a chosen genre. You might find that if you try too hard to contrive lyrics, you'll dry up, perhaps try being flippant but relevant. Find a random set of words that fit a line, get you head around the chosen subject and allow that throw away line to evolve into one you can use by writing subsequent lines underneath it which mirror the phrasing and maybe the rhyme or vowel sounds that exist in that initial line and you might well find that it triggers some random gems that you can collate and trim until you have something which you can use to form your lyrics.
Good luck
Tim