As we conclude the first scene Macbeth has finally come to the drastic decision to murder King Duncan and his son Malcolm, in order for him to be first in line for the throne and receive the title of King. Many individuals pressured him into making this decision, the most forceful of course being Lady Macbeth. .
At the beginning of the play the three witches seem to be able to predict the future. When Macbeth meets the three witches they tell him that he will become Thane of Cawdor and later, go on to become the king. "All hail, Macbeth! Hail to thee, Thane of Cawdor! All hail, Macbeth, that shalt be king hereafter!" (I, iii, 52-53).
After the witches have spoken those words Macbeth becomes rather interested in finding out if it will actually come true. When the witches first predict that he will become Thane of Cawdor he becomes somewhat gluttonous and believes that being given the title "Thane of Cawdor" is not enough for his acts of courage, for winning the battle, he believes he deserves more much more. .
Secondly, Macbeth starts of saying that he is going to allow time to go by and whatever happens to King Duncan happens. He doesn't want to get in the way of fate and consequently won't change the outlook by murdering Duncan or his son. However towards the end of the scene, Lady Macbeth convinces the King into having a complete turn around, telling him that if he doesn't kill Duncan then he will never become King. .
Lady Macbeth talks Macbeth into thinking covetously " and you shall put this night's great business into my dispatch, which shall to all our nights and days to come give solely sovereign sway and masterdom." (I, vi, 80-83). Lady Macbeth is trying to make it seem that killing King Duncan is the best thing for Macbeth, however he doesn't know that the only reason she wants him to be King is so that she can also be heir to the throne and have the title of Queen. .
Lastly, Macbeth also has a huge influence in the decision of murdering King Duncan.