“I had rather be a dog and bay the moon than such a Roman”

Implying that he would rather be a dog than such a Roman. This is because the dog is waiting for a response from the moon and that is impossible so he is also trying to say that he would rather be a dog trying something impossible than such a Roman like cassius.

Moon: A stymble for the impossible

Metaphor: Dog and bay the moon. It is a metaphor because he doesn’t actually wanna be a dog he is just saying that he would rather be someone trying to do the impossible then to be a man like Cassius.