Macbeth is a play whereby perversion of values take place. Like the witches' chant of "Fair is foul and foul is fair, hover through the fog and filthy air", it suggests that they are chanting the curse on Macbeth- from a good man to an evil man, who thinks that doing good is evil and doing evil is good.
The play is where temptations rule over one's moral values, as supported by the fact that for kingship, Macbeth turned evil to murder the King of Scotland. Macbeth was initially an upright man, a brave warrior. Upon the Witches' prophecy, Macbeth was tempted to murder for the crown. While the Witches' prophecy acts as a catalyst to Macbeth's kingship, it was Macbeth himself who should be responsible for allowing the evil side of him to over-rule the good side of him. Not to exclude that Lady Macbeth was also a catalyst to Macbeth's kingship as she wouldn't stop doubting his manliness and bravery, and would refer his hesitance to murder the King of Scotland as cowardice. As a man who loves his wife, Macbeth would obviously be mentally tortured to prove his manliness and that he has no fear.
While the play is filled with blood and gore, the play also leaves minor characters like Banquo, Macduff and other soldiers in the dark about Macbeth's deep and dark desires which eventually led him to numerous murders of the people who could actually see through his evil side and were standing in his way. The significance of this point is such that it snowballed to a vast increase in Macbeth's immoral fibre and chutzpah to incessantly harm and kill, leading to more blood in the play.
The Witches are evil to start the fire, but they are somewhat smart for being able to tempt Macbeth to do evil, only for his own good. Also, the Witches showed aspersions to Macbeth which, to any normal bring, would sound ridiculous and fallible. For example, the Witches told Macbeth that "no man born of woman can harm Macbeth". It sounded erroneous as all men are born of women by natural birth. It has never occurred to Macbeth that a man born by cesarean would murder him. The extreme evil side of the Witches somewhat fooled Macbeth, causing more evil to overrule himself.
Lady Macbeth, too, is a very evil character in the play who merely wants the best for her husband. One cannot conclude that Lady Macbeth is evil, as it only showed true in the first part of the play. Towards the end of the play, Lady Macbeth plunged into depression out of guilt. One cannot say that Lady Macbeth is not evil, either, for she was the one who dared Macbeth's manhood, insulted him by referring his hesitance to cowardice and finally managed to convince Macbeth to murder Duncan for kingship. The nature of evil in Lady Macbeth was very strong at the initial stages of the play, but evil transformed to guilt and blame for oneself, causing Lady Macbeth's death. The significance of this play is such that evil will be revenged. It is implied that the evil digs his own grave.
Macbeth was an evil man throughout the play after the first murder. He just could not stop, but to keep killing. As he thinks that another murder will cover up the previous murder, Macbeth did not want to stop killing- thus making himself more evil after each murder he engages in. In this play, therefore, evil somewhat increases with every evil deed.
In the play Macbeth, William Shakespeare compares temptation to moral values and evil to good (vice-versa). Such comparison allows readers to know how evil eludes and how evil harms himself and then perish. In this play, the nature of evil is described as a domino effect- that when one starts killing, he may never be able to stop. Macbeth is a play of blood and gore which ends with the evil being defeated. It is a play about a tyrant who ought to be punished.