Many critics believe that these similarities in the way they lead their people is a foreshadowing of what will happen to Malcolm. After all, much is left unanswered at the end of the play. What happened to Fleance? What about Donalbain? Readers are left to wonder if Malcolm will be overthrown in the same way his father was, perhaps because he trusts to much or isn't careful enough in his distribution of favors.
Duncan is grateful for the loyalty of his warriors and subjects. he is quick to reward those who perform well with titles and other tokens of appreciation. He fully trusts Macbeth and Lady Macbeth when he goes to their castle, and he has nothing but compliments for her and her hospitality.
Malcolm is much the same way. During the scene where the armies are preparing to march up to Macbeth's castle, he uses words charged with positive connotations and it is evident that God is on his side for the battle. After the battle and Macbeth is conquered, Malcolm, like his father, gives a speech of thanks and rewards those who performed well.