The supernatural plays an important role in Macbeth. To what extent does it motivate Macbeth's actions?

In the play, the witches whispered into Macbeth's ear promises that in which he first denied. They foretold that he would be the Thane of Glamis (which he already is), Thane of Cawdor, and King hereafter. As we both know, he became Thane of Cawdor which sparked something in him. He looked forward to becoming King, but he would have to kill Duncan in order to do so. Thus, the witches ignited the fuel for Macbeth to begin down his path of evil and murderous deeds. Banquo's ghost alone provokes fear within Macbeth that he might have vengeance against those responsible for his death (Macbeth). This drives him once again to the witches, who allow him to speak to the three apparitions. Each one gives him hope of invincibility (if you don't see it, look back again at the conversations between Macbeth, the witches, and the apparitions at the witches' haunt).

So to sum it up, the witches gave him the drive to kill, the ghost gave him fear and fright for his life and a need to draw from the witches' predictions, and the apparitions give him a falsified sense of protection and security.