When the play opens we learn that Macbeth is a great warrior and has served King Duncan well. He has led Duncan's troops in the defeat of a traitor, the Thane of Cawdor, and has proved himself loyal to the crown. However, with the witches' prophecies, Macbeth, once satisfied with being the greatest of Duncan's lords, becomes greedy for power. Having proved himself a great warrior and leader, it is difficult to accept Macbeth as power hungry or easily manipulated. However, when the first of the prophesies comes true, that he will be Thane of Cawdor, Macbeth begins to believe that he will, indeed, become king.
When he returns home, his wife immediately begins pressuring Macbeth to make his kingship happen. Macbeth, the once great leader and warrior, allows himself to be manipulated by his wife, who accuses him of being spineless and weak if he will not kill Duncan to become king. At this point, Macbeth has changed from a strong, loyal warrior and leader to a manipulated weakling. When he questions whether he can kill Duncan, Lady Macbeth berates him tells him he will be no better than a coward if he does not murder Duncan.
Once Macbeth is king, we see another change in his character. He begins killing anyone he feels may be a danger to his reign. He kills his best friend Banquo, he tries to kill Banquo's son, he kills Macduff's family - innocents - and he becomes a tyrant. He seems to have lost all of the levelheaded, strong leadership qualities he showed when was one of Duncan's thanes, and he is now a coldblooded murderer who is king with a reign of terror. He returns to the witches, showing he has embraced the dark arts, and his future decisions are based on their prophecies, making him believe that he is invincible. He becomes cocky and vicious, and controls his subjects through only fear and tyranny.
Macbeth goes from being a loyal soldier to a bloody tyrant.
At the beginning of the play, Macbeth’s praises are sung before Duncan. The bloody sergeant talks about how he heroically defeated the traitor Macdonwald. Duncan is so impressed that he confers upon Macbeth Macdonwald’s title: Thane of Cawdor.
Macbeth should be pleased with his promotion. However, on his way to report to Duncan he is waylaid by three witches. They greet him by name and also call him two other names: Thane of Cawdor and King of Scotland. He scoffs it off, until Ross greets him as Thane of Cawdor. Asking why he is being dressed in “borrow’d robes,” Macbeth demands to know what is going on. He is told of the promotion, and expects to be named king as well. When he is not, he gets angry.
The Prince of Cumberland! That is a step(55)
On which I must fall down, or else o'erleap,
For in my way it lies. Stars, hide your fires;
Let not light see my black and deep desires… (Act 1, Scene 5)
Macbeth has told his wife about the prophecies, and she expects him to take action. Killing King Duncan is the only way, she assures him. She plans everything, but he is still nervous. He does not really want to kill the king, to whom he has been loyal.
He's here in double trust:
First, as I am his kinsman and his subject,
Strong both against the deed; then, as his host,
Who should against his murderer shut the door… (Act 1, Scene 7)
Macbeth imagines a bloody dagger hanging in front of him, and decides that means he is supposed to kill Duncan.
The murder changes Macbeth. At first he is still unconfident. He imagines he hears witnesses accusing him. He accidentally takes the bloody knives with him instead of leaving them as incriminating evidence. Yet he grows bolder, killing the guards as well.
Macbeth has become more and more confident in killing, but also more paranoid. He hires murderers to
Kill Banquo because he observed the prophecies and is also a threat because his heirs were to be king. Then he sends them to kill Macduff’s family. Macduff’s wife and son are killed.
Lady Macduff has begun to worry about her husband. She has created a monster. He now has no qualms about killing, even women and children. In battle, Macbeth is confident. New prophecies have made him feel invincible. When the supposedly impossible prophecies like moving forests come true, he loses his nerve. He is a coward.
Macbeth's easy transformation shows that he was always ambitious. He just needed a little push. Once he has begun, he cannot stop himself. Once he has power, all he can think about is not losing it.