The main desire that motivates Macbeth in William Shakespeare's play seems to be ambition. This is a normal value. Most people want to make something better of themselves. A bagger at a grocery story might want to become a cashier, or a computer programmer a project lead or manager. Ambition in and of itself is not always bad. Normally, however, our ambition is restrained by social norms. We don't kill our bosses to get their jobs.
In the case of Macbeth, however, he has more than the ordinary share of ambition, to the point where morals, religion, and social norms barely restrain him. He refers to this desire for wealth and power in the lines:
... Stars, hide your fires;
Let not light see my black and deep desires.
The prophecies by the witches, however, and the urgings of the equally greedy and ambitious Lady Macbeth lead Macbeth to act on his desires rather than repressing them. What makes the play particularly powerful is the way that it illustrates the point that removing fear of negative consequences results in people showing their true moral nature.
Macbeth is motivated first by the need to please his wife as she persuaded him to kill King Duncan by telling him that she loved him enough to kill the baby she desired so much while she was nursing and asking if he loved her enough to kill the King. He is then motivated to continue killing by his quest for power and the need to continue to hide his deeds.