One of the big ideas we talked about was if Macbeth hadn't married Lady Macbeth would he have gone on a killing spree in order to secure his throne? I think he wouldn't have done so many killings. People's true character is bound to come out sooner or later, and in Macbeth's case it happens sooner. With Lady Macbeth in place, she was such a powerful force that it kinda happened against his will.
I think this is part of theme, in that there is no normal. We see it taken to the extreme here but when the characters try to cover up their mistakes or try to make everyone else seem more out of place.