In the play Macbeth it was fear that was the mainmotivating factor that influenced the outcome of the play. This can be proved by the subsequent murders that followed after Duncan's, why were these committed?

remembered the witches' prophecies. They claimed that Macbeth would be

King, but it would be Banquo's children that would follow after him.

This made Macbeth very angry, he risked everything to become King and

after him none of his family will follow.

Only for them; and mine eternal jewel

Given to the common enemy of man,

To make them kings, the seeds of Banquo kings!

[Act III, S I, L 72-75]

      Here Macbeth realizes that if something is not done to Banquo,

then his sons will become King. Macbeth can't have this, he's already

worried that his soul will go to hell for what he's already done. His

fear become evident in this scene also, "But to be safely thus: our

fears in Banquo Stick deep;" [Act III, S I, L 53-54] Macbeth then has

Banquo murdered, however his son Fleance escapes in the attack. Next

Macduff refuses to accept Macbeth as king and flees to England to join

Malcom. And also the witches tell him to beware of Macduff, which

angers Macbeth and drives him to kill Macduff's family. More fear of

losing the impending battle with England, makes Macbeth start doing

anything that will give him an edge in the final battle. Macbeth's

fear is starting to consume him, he can no longer sleep and is ravaged

by guilt over what he's done.

As well Lady Macbeth is being comsumed by fear and guilt, she is

slowing losing her sanity. This is a result of her not being

able to handle what she has done to Duncan. As shown in this quote

Out, damned spot!out,I say!One;Two:why,

then 'tis time to do't. Hell is murky. Fie, my lord,

fie! a soldier and afeard? What need we fear who knows

it, when none can call our power to account?

[Act V, S I, L 32-35]

      Here Lady Macbeth is trying to wash out what she sees as being

blood on her hands. As well she mentions hell an obvious fear of going

there for what she has done. At the start Lady Macbeth was the one

pushing on Macbeth to kill Duncan but as the play goes on she becomes

weaker as Macbeth becomes stronger, Macbeth isn't troubled by what he

has done to the extent Lady Macbeth is. Her role in the play slowly

becomes smaller and smaller as she ends up being driven mad by the

guilt and soon can no longer take, and ends up taking her own life

hoping that her torment will end now that she is dead. "The Queen, my

Lord is dead" [Act V, S 5, L 18], Lady Macbeth takes her life right

before the battle against the english is about to begin. This taking

of her own life demonstrates her fear and in the end what that fear

can do to a person.

      Now we come to the witches prophecies, these are a main source

of fear for Macbeth, after all where has he learned everything from.

With each new vision, Macbeth falls deeper and deeper into an evil

spiral. From the witches first prediction of Macbeth being king, which

made Macbeth kill to become king. As well as Banquo's children

becoming kings, this scared Macbeth as I previously mentioned. Also

when he went back to see the witches he gained some more knowledge,

"Macbeth! Macbeth! Macbeth! beware Macduff; Beware the thane of Fife."

[Act IV, S I, L 77], well now that Macbeth has heard this, he believes

that he must kill Macduff, however he learns that Macduff has fled to

England, so Macbeth desides to kill his family. Next in the cave

Macbeth is told he can't be killed by any man born of woman, well this

gives him confidence that no matter what the English will not defeat

him. And he is also told that he will not be defeated until the trees

of Birnam Wood move towards his castle. He has put all his faith in

these prophecies, what the witches say must be true because of the

first prediction.

      In conclusion you can see what fear can do to a person, it made

Macbeth mad for power which he ended up getting. But after the first

of his crimes the rest became easier for him, pretty soon he'd just

order it and not think twice. That was not the case when he first

murdered Duncan. All though the play his fear of being caught, and the

witches prophecies coming true make him do all these evil deeds. Fear

had become the main movating factor in the play. Hopefully you have a

better understanding of the play from all this.