You might like to think about Act I scene 2, which is when Duncan receives reports of how the fighting of his soldiers against the invading army supported by the treacherous Thane of Cawdor is going. In response to being informed about a fresh sally into battle by the Norweigian Lord and his troops, Duncan asks the Messenger if this vigorous renewed assault "dismay'd" Banquo and Macbeth. Note how the messenger responds:
As sparrows eagles, or the hare the lion.
If I say sooth, I must report they were
As cannons overcharg'd with double cracks;
Doubly redoubled strokes upon the foe:
Except they meant to bathe in reeeking wounds,
Or memorise another Golgotha,
I cannot tell--
The way in which the Messenger responds with obvious sarcasm, saying that Banquo and Macbeth were frightened like sparrows could frighten eagles, clearly emphasises Banquo's bravery. Also, consider the way in which they responded to the fresh attack by "redoubling" their efforts in this perilous situation, that could have overwhelmed them.