First, decide what you are going to be arguing about masculinity and feminity and how it is used in the play. What is your point going to be? What position are you taking? This is going to be your thesis (topic + position).Once you have a clear thesis, you should have two or three big points to make that prove your thesis. That is what will hold your essay together.
Do you think Shakespeare had a reason for messing with the notions of masculinity and femininity (was there a point in all that?) Does the confusion over gender echo the confusion in the social order? Do you think the fact that all of the parts, male and female, were played by male actors had anything to do with how femininity and masculinity were presented? Is there an ideal "male" and "female" role represented in the play? Could something be made of the fact that both of the Macbeths seem to miss the ideal for their gender?
Some of the motifs you might use...
- The idea that nothing is what it seems (fair is foul and foul is fair): the weird sisters (Banquo says that he wonders if they are men or women...he thinks they are women but their beards suggest they are not)...Lady Macbeth asking to be "unsexed" and filled with cruelty so that she can have the strength to kill Duncan, and asking for all that is feminine about her to be replaced
- The idea that fear is a feminine/ childish quality...Lady Macbeth questioning Macbeth's manhood when he decides he doesn't want to kill Duncan, and again after he does and he is tormented by his conscience (and yet again when he sees the ghost of Banquo). Also, when Macbeth finally does taste real fear, when he finds out that MacDuff was not "of woman borne", but was torn from his mother's womb, Macbeth's response is that he feels he has lost his manhood.