In the beginning Macbeth’s character is seen as a heroic soldier and the Thane of Glamis. Although this all changes once he his told by three witches that he will soon be Thane of Cawdor and even King. At first Macbeth is very doubtful of these statements. But once the first prophecy said by the witches comes true everything changes, especially Macbeth.
Macbeth has the ambition to become king but cannot do it himself. Lady Macbeth says it herself “Yet do I fear thy nature It is too full o' th' milk of human kindness To catch the nearest way: thou wouldst be great, Art not without ambition, but without The illness should attend it. What thou wouldst highly, That wouldst thou holily; wouldst not play false,And yet wouldst wrongly win. Thou'ld’st have, great Glamis, That which cries, “Thus thou must do,” if thou have it, And that which rather thou dost fear to do, Than wishest should be undone” (1.5.3-12). What she is saying is that Macbeth has the want to become king but he does not have aggressiveness and that he is to kind of a person to do what it takes for him to take the thrown himself.  
When the lady Macbeth hears that the king will be visiting their home this begins the change of Macbeth. During the planning and actual event of the murder of King Duncan Macbeth only plays a backseat role because he is hesitant and somewhat ashamed of himself for even considering killing the king while he is a guest in his home. But Lady Macbeth will not allow for them to let this once in a lifetime opportunity for Macbeth to become king pass them by. He does however follow through with this plan because of his weak-minded nature.
After Macbeth commits his first act of murder many things change.