What is the role of Banquo in Macbeth?

Banquo was great character , like Macbeth, is a great general. He is a military commander who fights side by side with Macbeth and distinguishes himself by his valour in the battle. When the Witches greet Macbeth, Macbeth starts but Banquo remains unmoved. When a part of the prophecy comes true through the news of conferment of the title of Cawdor on Macbeth, Banquo comments that the Witches were the agents of evil, who misled human beings by telling them certain : trivial truths and then betraying them in matters of vital importance. 

But later in a soliloquy he expresses his hope that the prophecy  relating to him may also prove to be true. The character of Banquo  obviously intended as a contrast to that of Macbeth. Banquo’s  wisdom and Macbeth’s lack of it find expression in their respective , responses to the prophecies of the Witches. 

Banquo’s firm loyalty to king Duncan is contrasted with Macbeth’s treachery. However, we must not forget that even Banquo does not unaffected by the Witches’s prophecy relating to him. When he finds that the prophecy with regard to Macbeth has proved true, he begins to toy with the thought that the prophecy with regard to himself may also prove to be true. Thus he does not by any means represent moral perfection, even though he shows a better judgment regarding the true character of the Witches.