Your request is pretty broad, and nature serves certain purposes in Shakespeare's writings, but isn't central to it--not like a romantic poet's, for instance.
A couple of angles do come to mind for your opening, though.
In Shakespeare's dramas, nature often reflects the chaotic or unnatural state of human affairs. In Macbeth, horses turn into cannibals and eat each other. In Julius Caesar, a lion wanders loose near the capitol.
In Shakespeare's poetry, nature is sometimes used as hyperbole for describing the beauty of a lover, but is also made fun of for being used for that purpose. Sonnet 18, for instance, the "Shall I compare thee to a summer's day?" poem, shows the silliness of comparing human body parts to elements of nature.
Depending on what you are going to write in your essay, something along one of the two above lines of thought might help you out.