What are some examples of personification in Macbeth by William Shakespeare? Why are these examples interesting and what do they add to the play as...

The previous answer does list some of the most memorable
examples of personification in Macbeth by William Shakespeare,
though of course you also asked for some commentary regarding their significance in the
play. Personification is giving human qualities or characteristics to things which are
not living or not human, and there are many examples in this
play.

Lady Macbeth is quite a dramatic and memorable woman,
and the things she says are often rather outrageous, which is in keeping with her
personality. In Act I of the play, she has just read the letter her husband sent her
about the witches' predictions and says this:

readability="5">

Stars, hide your
fires!

Let not light see my black and deep
desires.

This is an excellent
example of personification because the imagery is as dramatic as the intent. She is
asking the stars to do the impossible, to hide her ambition (her "black and deep
desires") from the rest of the world. Of course a star is a grand and powerful object
compared to a mere mortal, yet Lady Macbeth presumes to command them to obey her will.
Even more, she is asking them to be complicit (participatory) in her deception and
change the entire pattern of the world (make dark what is supposed to be light) just for
her. 

It seems like an outrageous request, and her
arrogance is rather astonishing. In the end, of course, no one but her husband does see
this awful ambition in her eyes, so perhaps the stars did cooperate, though obviously
not literally. This example of personification serves to show the size and scope of her
ambition--only the stars are capable of hiding it.

Macbeth
is a rather larger-than-life character, as well, making him the perfect match for Lady
Macbeth. He is ferocious in battle, loyal to his king (at least until he wasn't), and a
good enough actor to fool nearly everyone after Duncan's death. (Banquo is only
suspicious because of the predictions.) 

Despite his valor
in battle and his clear, overriding ambition, In Act II he is moved by guilt over what
he and his wife are planning to do to Macbeth. In scene ii he has to go finish the job
his wife was supposed to do, and when he returns from killing Duncan he is
distraught:

readability="21">

Me thought I heard a voice cry "Sleep no
more!

Macbeth doth Murder sleep"--the innocent
sleep,

Sleep that knits up the ravell'd sleave of
care,

The death of each day's life, sore labor's
bath,

Balm of hurt minds, great nature's second
course,

Chief nourisher in life's
feast--

Sleep is personified
several ways here. 

First, sleep is something that can be
murdered, as Macbeth thought he heard someone say he has murdered it. Of course it is
only his own guilt playing tricks on his mind, but the idea that Macbeth has murdered
sleep is a great personification here. Sleep is representative of peaceful rest, and
Macbeth has, indeed, killed that for Duncan.

Second, sleep
is personified here as something that can heal the body by doing things a person can do.
It knits up all the loose ends of worry and care into a neat edge or hem, it provides
the balm (soothing ointment) which can heal "hurt minds" and it provides nourishment for
every man's life. Obviously sleep is inanimate and can do none of these things on a
literal level, but when it is personified, sleep is able to provide healing and
peace--something Macbeth will not be able to find from this moment on in the
play.