Do you think Macbeth would have done what he did if he didn't hear about the prophecy. Macbeth was given ideas when he received the prophecies and the apparitions. He became very ambitious and thought about murder. He also had a sense of arrogance.
The idea of ambition was brought up when he was given the prophecy that eventually he will become King. Before the prophecy, Macbeth's loyalty to the King was unquestionable, he fought battles for him, and he would've given his life for the safety of the King. After hearing about the prophecy, Macbeth was given a different point of view on life. Macbeth was King Duncan's cousin and he was loyal to the King. Macbeth fought and won the battle against Norway. He did what he could to defeat the enemy and he came out victorious. As a reward for his bravery he was given the title Thane of Cawdor not because the witches gave it to him but because he did it himself.
He was Thane of Glamis and became Thane of Cawdor. He believed that the witches gave him the title and he thought that since being Thane of Cawdor he would eventually become the king. His ambitions took over him and he wanted to be more than the Thane of Glamis and he did by becoming Thane of Cawdor but what he wanted even more was to become the King. He wanted power.
Through the prophecy, Macbeth was shown that he could become greater and he was pushed to commit murder. Macbeth felt that in order for him to become King he would have to kill Duncan and with his murder Banquo's suspicions arose. Therefore, he would need to kill Banquo to silence him. He would also need to kill Macduff's family...