Macbeth's army consists of soldiers who stand in "forced affection," meaning they do not support Macbeth willingly or serve him out of respect or loyalty. In Act V, Angus describes Macbeth's army:
Those he commands move only in command,
Nothing in love.
In contrast, Malcolm's army is composed of men who fight passionately, united in their determination to destroy Macbeth, the tyrant who has stolen the throne of Scotland and plunged the country into misery. Furthermore, English soldiers have joined Malcolm in his fight, and citizens of Scotland have risen to swell the ranks of his army, as well. Macbeth notes that Malcolm's army is reinforced with "those that should be ours." The disloyalty of Macbeth's army is pointed out by Malcolm during the battle:
We have met with foes
That strike beside us.
Macbeth's army appears to be fighting for Macbeth, but in battle they deliberately miss when striking Malcolm's soldiers.