The final scene of Shakespeare's Macbeth is the culmination of the play, of course, and as such, it concludes various plot lines and themes.
For instance, the full extent of the witches' manipulative equivocation is finally revealed when the reader discovers that Macduff was delivered in the manner we today would refer to as a C-section, and thus was not literally born of woman. Macbeth's immediate reaction to the news is to recognize the extent of the witches' lies. This suggests a discussion on the extent of Macbeth's free will, the role of fate, and the question of who is to blame.
Macbeth's discovery and his immediate reaction--the loss of his courage--also leads into a second discussion point. Macbeth, though shattered by his discovery that he is not invulnerable, chooses not to surrender and to continue fighting. He faces his opponent and fights one-on-one in a fair fight. Is Macbeth being noble or demonstrating nobility here? Or is he just refusing to be paraded around in a cage and humiliated? If the latter, is this noble? To what extent does Macbeth demonstrate the tradition of a tragic hero as a noble figure?
The final scene also simultaneously clarifies and muddies the question of Lady Macbeth's death. The rumor is that she committed suicide, but the accuracy of the rumor is not addressed.