Act I

Scene i

Three witches discuss when they will next see each other and identify that they will meet with Macbeth when the battle ends.

Opening the play with witches sets a supernatural mood and marks the importance of their involvement. The scene is very short and they speak in riddles, yet the audience understands that the meeting will occur near the end of a battle and that they plan to use Macbeth for their mischief.

Scene ii

King Duncan and his eldest son, Malcolm, speak with an injured captain on the battlefield. The captain reports on their progress against the Norwegians, singling out Macbeth as particularly courageous. He credits both Macbeth and Banquo for their part in the victory. News comes from Fife via Ross, a nobleman, informing Duncan that the Thane of Cawdor joined the enemy, but the Scottish army were able to defeat the Norwegians and the traitors. Duncan announces that he will strip the title from the Thane of Cawdor and bestow it upon Macbeth.

The audience forms an idea of Macbeth as a valiant and loyal subject to the king, especially compared with the traitor Thane of Cawdor. This scene is also quite short and uses the backdrop of war to introduce the characters and highlight their attributes.

Scene iii

The three witches meet again. While waiting for Macbeth, they plan a shipwreck because a sailor's wife offended the First Witch. Returning home from the battle, Macbeth and Banquo meet the witches, who offer them predictions. They address Macbeth by his current title, Thane of Glamis, then Thane of Cawdor and then King. They give contradictory statements to Banquo about his status and happiness and foretell that his descendants will be kings although he will not personally ascend the throne. Macbeth doubts the witches' veracity (truthfulness) but before they answer his questions, they vanish.

Ross and Angus join Macbeth and Banquo to give them a message of thanks for their part in the battle and inform Macbeth of his promotion to Thane of Cawdor. Macbeth and Banquo discuss the witches' prophecy with regard to the news. Macbeth's thoughts pause on murder as the means to the kingship, but he still doubts the witches' intentions.

The beginning of this scene emphasises the evil nature of the witches. Shakespeare then uses the foundations for dramatic irony (knowledge the audience has that contradicts the action on stage or the characters' beliefs) that he set up in the first two scenes. That is, the witches' intentions regarding Macbeth, and his promotion, inform the responder's interpretation of Scene iii: they begin to realise the witches are not to be trusted.

The scene is set on open ground, neutral territory that the witches use to their advantage because Macbeth and Banquo are battle-weary and out of their comfort zone. Already, the audience may note the difference between the loyalty attributed to Macbeth by others in Scene ii and his privately disloyal thoughts.

Scene iv

Duncan asks after the former Thane of Cawdor's execution and remarks that he trusted him until his betrayal. Duncan thanks Macbeth and Banquo personally for their role in the victory and they declare their loyalty to him. Duncan then names Malcolm as his heir, obstructing Macbeth's path to the throne. Macbeth recognises Malcolm as an obstacle.