I can't write an essay for you, but I can give you some information and ideas about your topic. The supernatural does play an important role in the play; the appearance of the dagger in Act II, the appearance of Banquo's ghost in Act III, and the witches' various appearances throughout the play serve as intrusions of the supernatural world into the events of the play. All, with the exception of the dagger, are represented in physical form on stage. Interpretation of these supernatural elements has been subject to much discussion. Did the witches have the power to control Macbeth's future, or did Macbeth create his own future? Did the dagger really appear, or was it a figment of Macbeth's imagination and guilty conscience? Why does an actor appear onstage as Banquo's ghost? Why does Macbeth not speak to a ghost only he can see, just as he spoke to the invisible dagger? Is Banquo's ghost to be accepted as "real," whereas the dagger is not? Taking a position on these questions could create an interesting essay. Also, the eNotes links below should be very helpful.