In Shakespeare's Macbeth, the letter Lady Macbeth receives tells the audience a great deal about this Scottish hero—one of King Duncan's most trusted warriors.
First we learn that Macbeth not only met three old women, but that he believes they are witches, and that they have supernatural knowledge of the future.
We find that Macbeth wanted to question the women further, but they disappeared into thin air, right in front of him.
We discover that as the witches' first prediction that Macbeth would become the Thane of Cawdor comes true, Macbeth assumes that their prediction that he would one day be king is uppermost in his mind.
It is easy to tell that Macbeth loves his wife in the way he addresses her:
This have I thought good to deliver thee, my dearest partner of greatness...
It is equally clear that he is excited to share what meaning this news has for her:
...that thou mightst not lose the dues of rejoicing, by being ignorant of the what greatness is promised thee.
This small segment of the play shows how concisely Shakespeare writes: without coming straight out and telling us what he wants us to know, he uses the letter from Macbeth to his wife, and we learn a great deal about the main character of the play.