King Duncan- He had a lot of ambition for royalty, has high moral standards, and a ruler which he represents a Lion. Lions are known for their royalty by taking over the pack and leading the way. He wants what's best for his kingdom. We will establish our estate upon our eldest, Malcolm, whom we name here after the Prince of Cumberland; which honor must not unaccompanied invest him only, But signs of nobleness, like stars, shall shine on all deservers.—From hence to Inverness and bind us further to you. (1.4.39-49) Shows that he making everything apart of his throne and having nothing get in the way to achieve ultimate power. "This murderous shaft that's shot/ Hath not yet lighted, and our safest way/ Is to avoid the aim" (2.3.167-169) shows how things will go by for the best.
Lady Macbeth- She is very ambitious, craves for power, and a ruthless/strong person which kinda relates to snake like traits. Snakes are sneaky, strong of course and reckless when striking what they want. Lady Macbeth calls her husband "infirm of purpose," she refers back to the root meaning of "infirm": unsteady, "not firm." Macbeth's idea is weak; he fears the deed he's done. She seems to be the stronger and more ruthless of the two, as she forces her husband to kill Duncan and achieve the crown. Lady Macbeth's thoughts immediately turn to murder after the letter from her husband.