In Macbeth, much of the plot is hinged on chance. It is by chance that King Duncan decides to spend the night at Macbeth's home. King Duncan could have honored Macbeth without attending a meal at his home. In fact, it was such short notice until Macbeth and Lady Macbeth were short of help. Macbeth mentions that he and Lady Macbeth were unprepared for King Duncan:
Our wishes became the servants to what we lacked,
Which has worked out very well.
Noting that Macbeth and his Lady were unprepared signifies that it was by chance that King Duncan decides to dine at Macbeth's castle. Even more by chance, King Duncan decides to spend the night. This is a perfect set up for the murdering of King Duncan.
Another time the plot involves chance is when Banquo and his son decide to go riding. This sets up a perfect time to murder Banquo. Macbeth questions Banquo about his plans to ride:
Are you going riding you this afternoon?
Are you riding far?
Banquo responds that he is going to ride as far as time will allow him:
As far, my lord, as will fill up the time
between this meeting and supper.
This riding event is by chance. It gives the murderers a chance to kill Banquo. Banquo's choice to go riding creates a perfect time for the men whom Macbeth has hired to kill Banquo.
One other moment of chance happens when Macduff faces Macbeth in battle. Macbeth is forewarned by the witches that he cannot be killed by man born of woman. He declares to Macduff that he has a charmed life:
You’re wasting your efforts.
You may as easily slice the air that cannot be cut
With your keen sword as make me bleed.
Let your blade fall on weaker heads;
I have a charmed life, which must not yield
To one given birth to by a woman.
It just so happens that Macduff was not born of woman. By chance, he was born through cesarean birth. By chance, Macduff was "ripp'd" from his mother's wound. He proclaims to Macbeth in triumph that he just so happens to have been born by cesarean section:
Lose hope of your charm;
And let the genius whom you still have served
Tell you, Macduff was from his mother's womb
Delivered by caesarean section.
The plot of Macbeth is filled with events that happen by chance.