In Acts I and II of Macbeth, Macbeth and Lady Macbeth are integrated (share the same views) in their desire for power. Their marriage seems to be a practical means to a political end. Neither have married, it seems, for love or children. Rather, they seem intent are being collaborative power brokers, using the semblance of marriage for show.
Lady Macbeth knows that women have no independent power in Medieval Scotland; instead, women must live vicariously through their husbands. Therefore, she resorts to motivating Macbeth by any means necessary: she de-genders herself privately and calls out his manhood publicly. Then, she devises the plan to murder the king. Taken together, she becomes a persuasive accomplice, a validation of Macbeth's own secret desire, a Freudian id who sways him from away from the guilt of superego. Lady Macbeth, however, cannot cross-over into the violent world of men; she cannot stab Duncan herself, which shows that she needs Macbeth more than he needs her.
In Act III, after Macbeth has become King, the relationship changes from integrated to more segregated. There is a division of labor in the marriage. Her front-end work done, Lady Macbeth dissolves into the background and into mental illness. Macbeth does not consult her in the murder of Banquo; rather, he wants to surprise her with his own plan and execution. Macbeth goes on more killing sprees ("blood will have blood"), while Lady Macbeth cannot reconcile her guilt over the murder of Duncan, perhaps because he looks too much like her father.
While Macbeth continues to let his id run amok in Acts IV and V, Lady Macbeth becomes a sleepwalking superego, confessing her sins to her chamber-maid nightly. In the end, the blood and guilt are too much, and she uses suicide as the ultimate cleansing agent. Macbeth, though, is determined to fight to the death. Herein lies a major gender difference. Having been deceived by the riddles and plans of women, Macbeth resorts to what men do best: combat. His unremorseless soliloquy and show of violent defiance are but his final assertions of unadulterated manhood: he is no longer married to woman, God, or country; instead, he is a free agent thane hell-bent on nihilism.