I'm writing an essay on Julius Caesar and my theme is betrayal. What would I write for my introduction paragraph and concluding paragraph?

For the introduction introduced the play, bring up the meaning of betrayal and mention that Julius was betrayed. But don't explain it all there, you can go more into detail about that stuff in the following paragraphs. For the concluding paragraph you can briefly summarize what you had written, but don't bring up any new information at all.