In a word, the language is poetic. It is full of metaphors and hyperbole. It is as if the emotion the two young lovers feel is so full of emotion, it can't be contained in normal language. Instead, they must translate it, and use imagery, rhythm, metaphor, and language from other sources, such as mythology and religion. For example, in the first meeting, Romeo refers to Juliet (or perhaps just her hand) as "This holy shrine," starting a string of pilgrimage metaphors, as if he'd been seeking her his whole life, and as if she were the meaning of his world.