Try and think like My Chemical Romance. Or just let the words come to you. If you've listened to MCR long enough, you're bound to develop some kind of similar ideas.
They tell stories with their songs, so just pick a topic you think is appropriate and some songs! Also you can write songs about your feelings and life as well.
Well, you'd have to have a mind like Gerard Way to do that. Well, I'll try and break it down for you, because I'm also an inspiring songwriter. The one pattern I notice in all of MCR songs is that...
Gerard often says that the lyric "How wrong we were to think that immortality meant never dying" from Our Lady Of Sorrows is his favourite, maybe that's it.