In Act 1, scene 2 of "Macbeth," Scotland is at war with the Irish under Macdonwald. Banquo and his fellow Scot general Macbeth, who personally defeated Macdonwald himself, are praised before King Duncan for their bravery and skill. The king also receives news that the thane of Cawdor has been defeated, to which he responds by bestowing the title upon Macbeth as a reward for his heroic display in battle.
Macbeth does not learn of his new title as thane of Cawdor until the next scene. In Act 1, scene 2, he is still returning from battle.
This scene establishes the title character as a powerful and respected warrior — a hero in the classical sense. This is important to lay the foundation for his tragic fall from grace, a key characteristic of Shakespearean tragedy. Macbeth's stature as a warrior is illustrated through the use of similes in this scene, with he and Banquo being likened to eagles and lions. The latter of these animals actually features on the Scottish king's coat of arms, further linking Macbeth with greatness and nobility.
Through the account of his heroics given to Duncan, this scene also foreshadows Macbeth's demise in graphic detail. As the captain describes it, Macbeth impaled Macdonwald's head upon the battlements.