In the beginning of the play, Macbeth is a picture of goodness, while Lady Macbeth is seen as being truly evil. Lady Macbeth sees immediately that the quickest way for her husband to become king would be for them to kill Duncan. However, she also recognizes the fact that Macbeth is too "filled of the milk of human kindness" to kill the king. She convinces him to go through with it by challenging his manhood. He kills the king, but feels guilty. She tells him to forget about it.
Their personalities begin to change. Towards the middle of the play, they are more equal. Macbeth is accepting the murder, and his wife is beginning to wonder if they should have done it or not. At this point, they have not yet completely switched roles, but they are closer to feeling the same abut the murder than they were.
Near the end of the play, there is a clear exchange of emotions. Lady Macbeth's sleepwalking scene shows how she now feels very guilty about the situation. She no longer knows how to deal with these feelings, and kills herself. Macbeth is now so oblivious to emotion that he does not shed a tear for Lady Macbeth. he says how he will not think about his actions anymore. He will act on impulse, and not ponder the morality of his actions. He later dies while still fighting and killing to be king.
Their roles are as if there wree sides to it. Macbeth starts out on the good side, and Lady Macbeth on the evil side. As they move forward into the opposite side, they pass each other. This is when they are more equal. They continue to move forward, and now away from each other. They stop, and find themselves on the opposite side to which they started from. Macbeth is now evil, and Lady Macbeth is more good.