Macbeth is a heroic character at the beginning of this play "unseaming men from the nave to the chops." He has much potential as a warrior, and has great love and respect for his country. Coming back from battle one day, he is greeted by three witches, who are known to have great and terrible powers to foresee the future. They meet him with predictions when they greet him as Thane of Glamis' (his present title,) Thane of Cawdor' (a higher rank) and King of Scotland. Macbeth is extremely intrigued by what they say to him, especially once he learns that he has earned the title of Thane of Cawdor' for murdering the traitor Macdonwald. Macbeth believes that since the first two prophecies became reality, the third one must materialize also. But instead of waiting to see it happen without interference, Macbeth takes it upon himself to make sure that the third prophecy comes true. These prophecies prove to be the first bits of motivation for Macbeth's actions (mainly murders) throughout the duration of the play.
In addition to the prophecies, Lady Macbeth is a firm generator of motivation for Macbeth's actions. Once she hears about the prophecies, she becomes determined to do whatever is necessary to become Queen on Scotland. In the beginning of the play, she proves to have a stronger willpower than Macbeth, and is arguably the first valuable piece of motivation for his actions, since Macbeth is hesitant to commit the murder on the basis of the prophecies alone. Lady Macbeth uses her cunning, persuasive manner to convince Macbeth that murdering Duncan is the right thing to do. Lady Macbeth also taunts