I have to divide the post in two parts for its length.
In the play Macbeth, the supernatural elements primarily include the “weird sisters” and their gang. These elements are used to pave way to show Macbeth the path of his ultimate downfall.
The three witches instigate Macbeth's inner ambition and greed by luring him. And this they do through their so-called prophecies. The predictions of the witches and the apparitions are nothing but equivocations in the name of prophecies. The witches, at first, tell Macbeth that he would be the Thane of Cawdor and the King of Scotland soon. This is not something extra-supernatural they do, since, it is a matter of common-sense that, Macbeth, if he would have fought courageously and shown his man-of-the-battle attitude, he would definitely get rewarded, and if he continues to go after his ambition, would be the king possibly. Later, the apparitions prophesy that the no human born of women can kill Macbeth ever, and he would not be killed unless Birnam wood would come closer to his fort. The first prophecy is a lie in a sense that, Macduff, who is born of his dead mother's body via surgery, kills him. The second one is an equivocation also, since, though Birnam Wood does not come closer, yet the soldiers of the opposition hide them under the leaves of the forest, and this makes him think as if the forest itself is moving towards him, and he loses all his hope and courage to fight further. It is clear hence that, what the prophecies told was half-truth to destroy Macbeth. Ambiguity they create in Macbeth's mind throughout the whole play. Ambiguity, or conflict between appearance and reality, is one of the key themes in this tragedy. The witches just equivocate in a dubious way; implying that, lie in a way which seems apparently true. And this they do solely to win his trust and make him a devil like them.
The witches know that, Macbeth is an ambitious man who just needs a spur in order to rouse his ambition and let it develop fully to achieve his end. They show him what he wanted to see. They tell him what he wanted to hear. Their prophecy awakens his inner demon and instigates his voracity. Macbeth is thus deceived. He is told that no human born of woman can kill him; neither would he be killed till the Birnam Wood come close to his fort. Later, when he finds that the Birnam Wood does not come nearer, rather soldiers hiding themselves under leaves come closer, and Macduff is found to be born out of surgery probably because of his mother's illness or death, he understands clearly that, he has been deceived by the witches' dubious prophecy. In act 5, scene 7, disillusioned Macbeth tells to Macdufff: "Accursed be that tongue... / That palter with us in a double sense, / That keep the word of promise to our ear/ And break it to our hope." So, it is clear that, the witches prophesies contributes to influence and instigate him towards evil deed.
In fact, Lady Macbeth's greed and cruelty increases more once she is aware of the witches' prophetic statements.
There is a strong role of a supernatural force in Macbeth. The witches who had the power to see the future, the ghosts and of course the bloody dagger that appeared to Macbeth before going to commit his murder to the king . all these seems to be supernatural. The Three Witches are the strongest of the supernatural powers in the play. They made prophesies that effected Macbeth and moved him toward killing the king and his best friend and finally those prophesies caused his death .
The Witches didn't predict that he will commit murder to become the king but only that he will become king. The Witches knew how he will get to be a king . The Witches have the biggest affect on Macbeth because they are the ones who told him their prophesies. The Witches said that no man born from a woman's womb can defeat Macbeth, that made him feel unbeatable. However, Macbeth does not realize that Macduff was born unnaturally and he will be the one to kill him.
Macbeth has a vision of a dagger just before killing the King. This vision of a bloody dagger is another example of the supernatural. This dagger encouraged or "pushed" Macbeth to kill the king. Shakespeare used the supernatural to add an evil side to the play to attract the people. The supernatural is used in all places where evil is present.
Banquo told Macbeth that he suspect him of killing the King . Macbeth feared being murdered and being discovered of killing King Duncan. So he killed Banquo and at the same night he was invited to a feast. He saw Banquo's ghost there and that made him went mad and almost crazy though he is the only one who can see the ghost . This supernatural scene is very important since it is one of the first signs of Macbeth's fear and guilt.
The supernatural theme is a very important one in “Macbeth”. Otherwise the play would not be as great as it is now, and Macbeth could not be beaten . Macbeth caused his own death when he relied on the supernatural.
Besides, some more supernatural incidents take place in the play. For instance, an owl kills a falcon, and Duncan’s horses eat one another as described in Act 2, Scene 4. This chaos arisen in nature forecasts the upcoming trouble to Scotland.
Lastly, a minor but hardly unignorable supernatural fact is the healing power of the King (4.3) which is considered as a “strange virtue”. This indicates that going against the divine power of kings was considered as a sin at that time. So, Macbeth is a sinner in that context too.