Romeo and Juliet is chock full of poetry, especially love poetry. The first time the couple meets, their dialogue forms a perfect Shakespearean sonnet. The famous balcony scene? Well, it's full of great lines that have since made their way into Hallmark cards and pop music lyrics. Shakespeare's not just showing off his skills – the play takes a pretty self-conscious look at the conventions of popular sixteenth-century poetry even as it participates in the art form. The clearest example of this is Romeo's role (at the play's beginning) as the kind of cliché lover that frequently appears in Petrarchan sonnets (love poetry inspired by fourteenth-century writer, Francesco Petrarch), which was all the rage when Shakespeare wrote Romeo and Juliet (c. 1595).
Although Romeo's love musings are cliché and unauthentic at the play's beginning, his poetry improves over the course of the play as he grows deeper in love with Juliet.
Shakespeare makes fun of cheesy love poetry in Romeo and Juliet, but he also suggests that, when love poetry is sincere, it's the most powerful and authentic mode of human expression.