what is theme in macbeth ?

You have this under the wrong heading. Anyway, there are a few themes to Macbeth. I think that unchecked power is a big one. "Absolute power corrupts absolutely" and that sort of thing. Macbeth gets a taste of power and his little brain goes into overdrive. Macbeth will keep his power at all costs. He doesn't do this because he simply likes being king but rather power itself becomes its own intoxicant. As soon as Macbeth finds out he is Thane of Cawdor he buys a one way ticked to paranoid crazy land. Macbeth sells his soul for power and leaves a trail of blood behind him,

"I am in blood

Stepped in so far that, should I wade no more,

Returning were as tedious as go over."

There are other themes as well. Lady Macduff comments on how evil seems to have an easier way into mens' hearts. There is also the close connection between Kingship and tyranny.