I love this kind of assignment. The first step you should take is to make a list of all the really major events that you could cover in your rap. Here is a basic outline:
- Witches make prediction
- Macbeth debates killing the King, but Lady Macbeth convinces him to go for it
- Macbeth kills King Duncan
- Duncan's sons flee Scotland
- Macbeth hires killers to kill Banquo and Fleance (Fleance escapes)
- Macbeth starts to become super paranoid and guilt (example: he sees Banquo's ghost at the dinner table)
- Macbeth visits the witches again for an update from the spirit world. A big floating spirit head warns him against MacDuff. The spirits also give him some pointers that make Macbeth feel pretty invincible, like he cannot be killed by a man born of a woman.
- Macbeth hires killers to murder MacDuff's whole family.
- MacDuff meets up with Malcolm in England. He hears of Macbeth killing his entire family and vows revenge.
- Lady Macbeth is not well. She sleepwalks and tries to scrub invisible blood from her hands. Good catch phrase from this scene? "Out damn spot!"
- Macbeth prepares to fight to the bitter end, as does the opposing forces of Malcolm, MacDuff, and pretty much all of the good guys who feel like Macbeth is a power-hungry tyrant.
- Lady Macbeth dies. She probably killed herself, and Macbeth's response is that she could have picked a better time.
- MacDuff fights and kills Macbeth. When the fight first began, Macbeth was over-confident because of the spirit's revelation, but MacDuff informs him that he was actually delivered via caesarian. MacDuff cuts off Macbeth's head.
You also have many potential great lines from the play that you could also incorporate into the rap, like the witches' chant from Act I, "Fair is foul, and foul is fair," which you could use to incorporate the theme of appearance versus reality.