Malcolm's Promotion and Macbeth's Dark Turn
Duncan makes a crucial announcement that changes everything - he names his son Malcolm as "Prince of Cumberland," making him heir to the throne. This is the moment Macbeth's world shifts completely.
Duncan uses beautiful imagery about planting and nurturing Macbeth and Banquo, promising that "signs of nobleness like stars shall shine on all deservers." He's genuinely trying to be a good king who rewards loyalty. Duncan even invites himself to Macbeth's castle, showing complete trust.
But everything changes with Macbeth's aside (private thoughts spoken to the audience). Malcolm's promotion is "a step on which I must fall down, or else o'erleap" - he sees it as an obstacle to overcome. His chilling line "Stars, hide your fires, let not light see my black and deep desires" reveals that dark ambition is already forming.
The scene ends with Duncan praising Macbeth as a "peerless kinsman" - the perfect relative - whilst Macbeth is already planning treachery. Shakespeare's dramatic irony here is devastating.
Remember this: This scene shows how ambition can corrupt even loyal people when opportunity presents itself.