What is a good thesis statement for Macbeth, Act 5?

The famous American playwright Arthur Miller, who is best known for his play Death of a Salesman,  made the following observation:

The essence of all drama is this: The chickens come home to roost.

In Miller's Death of a Salesman, Willy Loman and his entire family have to suffer because of the mistakes he made over all the years. He ends up committiing suicide. His two sons are failures and despise him.

In Act V of Shakespeare's play the evil deeds of Macbeth have brought an English army of ten thousand men to Dunsinane, along with his nemesis Macduff, and he has been deserted by many of his subjects. He tells himself:

I have lived long enough. My way of life
Is fall'n into the sere, the yellow leaf,
And that which should accompany old age,
As honor, love, obedience, troops of friends,
I must not look to have, but in their stead
Curses, not loud but deep, mouth-honor, breath
Which the poor heart would fain deny and dare not.

I think you could quote Miller’s definition of drama in your thesis statement and then go on to explain how the chickens have come home to roost in Macbeth. In Shakespeare’s play the murder of King Duncan takes place in the castle at Dunsinane, and in the last act the enemies Macbeth has made have come to Dunsinane for their revenge.

The analogy of the chickens coming home to roost is ironic and proverbial. It applies to all of us. Whatever misdeeds or mistakes we make in life will come back to haunt us even if it takes many years.

What is a good thesis for an essay on Macbeth by Shakespeare?

William Shakespeare's Macbeth is full of potential themes, so the key is to pick the one with which you are most comfortable and familiar and start with that. I've attached an excellent eNotes site which discusses the major themes in the play, but a quick review would have to include the consequences of too much ambition (which results in not only Duncan's death but in many others, including the Macbeths) the effects of guilt (which is different in each of the Macbeths), and the role of fate (as in the witches' predictions). 

One topic which interests me is the constant theme of reality vs. unreality. Shakespeare consistently presents us with many examples of this, even in the beginning of the play when the witches say,

“Fair is foul, and foul is fair."

Words like these are spoken throughout the work. This is a pervasive theme in throughout the play, and at the center of it is the role of the witches. Are they really invested with the power to predict the future or do they just seem to be? (There is another possible them: the role of the witches in this story.)

The Macbeths seem to be gracious hosts for King Duncan, but they are actually his murderers. Lady Macbeth even gives this advice to her husband:

“Look like the innocent flower,
But be the serpent under it.” 

Another interesting idea is a compare/contrast essay between the two Macbeths, or perhaps you could answer my favorite Macbeth question: whose sins were worse, Lady Macbeth's which were covert, or Macbeth's which were overt? Really, the play is replete with potential ideas. Consider anything you found intriguing or instructive and you will be able to write from a point of interest. 

Whatever theme you connect with should be clear in your own mind and supportable by evidence from the text. I have also included a helpful site for writing this type of essay. 

I don't know if your thesis statement has to begin with Macbeth being evil in the play. If not, I would change it to "Macbeth's ambition drives him to evil acts in the play with unfortunate consequences for himself, others and the kingdom." But if you have to word it the way you describe, you could say that "Macbeth, being evil in the play, gives in to his overwhelming ambition, causing death and destruction throughout the course of the drama." Then, of course, you would look for examples of ways Macbeth's ambition leads him into evil acts, such as murdering Duncan, Banquo, etc, and the effect this has on him and others. You might also want to contrast what Malcolm has to say in Act IV, scene iii about the characteristics of a good king with Macbeth's lack of ability to control his impulses—in other words, Macbeth's ambitious streak as a contrast to the humility and honesty of the good ruler.

What would be a good thesis for an essay on Macbeth as a moral play?

By strict definition, there is a type of play known as a "morality play" that was popular during the Middle Ages. Certainly this kind of play influenced the dramatic movement which was to become so popular in England during Shakespeare's time. And while there were other playwrights of that time, ostensibly Shakespeare has been the most enduring and influential.

A morality play was one that taught morals. It was rooted in theological values, though it did not use stories from the Bible to do so. The Roman Catholic Church exerted enormous power at the time when there was really no distinction between church and state; it was through these plays that the concepts of good vs. evil were presented to those who viewing the play, thus encouraging moral behavior. Often times presented on the backs of wagons in a village square (long before theaters). The plays...

...were more concerned with morality than spirit.

The struggle of morality revolved around evil and good battling over the "soul."

It is probably safe to assume that this kind of dramatic tradition affected not only Shakespeare, but all playwrights of his time, for this form of play was the "predecessor" of what became the dramatic movement of Renaissance England.

Is Macbeth one of Shakespeare's moral plays? Had we been discussing Hamlet, it would be an easy answer, for Hamlet himself, charged by his dead father's ghost to avenge his murder, asks himself if the ghost is truly that of his father, or a spirit bent on causing Hamlet to commit a mortal sin (killing a king) and losing his eternal soul.

In Macbeth, however, we need to look more closely. A major point is that Macbeth starts out as a brave and much-loved soldier for King Duncan, who is also Macbeth's cousin and friend.

Moral is defined as...

...expressing or conveying truths or counsel as to right conduct, as a speaker or a literary work...

Macbeth is riddled with what is generally called "vaulting ambition." This is his "tragic flaw."

I have no spur

To prick the sides of my intent, but only

Vaulting ambition, which o'erleaps itself... (I.vii.25-27)

He finds that he really does not have the desire to kill Duncan, at least not for the sake of money or politics, but his ambition will not allow him to be satisfied with what he does have—Duncan has greatly favored and rewarded him.

Macbeth is also squeamish with what he has done in killing Duncan:

MACBETH:

I am afraid to think what I have done

Look on't again I dare not. (II.ii.65-66)

This indicates that it does not sit well with Macbeth's basic nature; but as he continues to kill, it bothers him less until he knows there is no turning back. Macbeth is a conflicted man: he wants to be King for the power and position, but is does not naturally come by the treachery that it takes to take Duncan's life. It is Lady Macbeth's constant badgering and insults that drive Macbeth's sense of purpose.

If this were my assignment, I would write something like:

William Shakespeare's Macbeth tells the story of a seemingly moral man who loses his soul due to his treachery—not because it comes naturally to him, but because of an inescapable desire to be king.

I would write about Macbeth's moral character at the start (his valor, the arguments he gives his wife for not killing, etc.), his guilt afterward and how he deteriorates as a moral person in the rest of the play.

Additional sources:

http://www.enotes.com/macbeth/summary

http://dictionary.reference.com/browse/moral