What is the theme of the Reign of God?

I am writing a scripture essay, and my teacher is asking my to discuss the relevance of EACH three films Romero, One Another, and 20-20's Help from Beyond, but i really just don't understand what to write at all for this paragraph. Can someone please explain what the theme of the Reign of God is? And if you have seen any of those three films, if you intertwine your answer with my question that'd be great. I just need ideas on how to write this!