There are many themes that you can consider. Magic is a big theme in the play. Elizabethans would have been aware of good(white) and bad (black) magic. The character of Prospero would have been a bit of an enigma to audiences but, by the end of the play, would have regarded him as a practitioner of "good magic". Shakespeare, however, challenges audiences with the responsibility that magic gives. It also mixes magic and the natural elements as another dimension that mere mortals do not have access to.