Act I includes these key characters:
- King Duncan: His murder drives the play; his goodness makes Macbeth's regicide even more abominable.
- Macbeth: He is the central figure, the protagonist, in the play.
- Banquo: As a foil to Macbeth, Banquo is especially important; his murder later in the play shows Macbeth's further descent into evil.
- Lady Macbeth: As Macbeth's wife, her character is very important; she plans Duncan's murder and exerts tremendous influence upon Macbeth to follow through. Without Lady Macbreth, Macbeth might not have actually killed the king.
- Malcolm: As King Duncan's son, Malcolm is the rightful heir to the Scottish throne; after killing Duncan, Macbeth casts guilt on Malcolm and his brother, forcing them to leave Scotland; Malcolm will not give up until Macbeth is defeated.