You might consider giving some background on the purpose of a pun. Is it to relate to people? Is it to entertain? Is it to show hyperbole? As a teacher of high school boys, I find everyday that I have to edit my language just in case they might take my use of a word and think about it another way. For example, if I want to talk about something that is standing up rimrod straight, I avoid using the vocabulary of describing it as absolutely erect. Immature laughs would erupt throughout the classroom if I used that language. So, in writing an intro, you might think of a similar anecdote wherein you have had to watch your language because of others, or you might simply define the purposes of figurative as I asked you questions about above. Whatever your attention grabber or hook ends up being, after that connect the idea to what you have seen in both Macbeth and Romeo and Juliet.
Another idea might be to have the title: Words, Worlds, Words. If you look at this quick, you don't notice the difference between the 3 words, but reading slowly enough, you see a different word in the middle. That difference is represented by a single character of meaning but it completely changes things. The same is true when we see a pun or simile, when thought of one way, the connotation of the word might mean one thing, but when thought of the other way, the denotation of the word means something else entirely. You may have to use an example to demonstrate this.