What dramatic purpose is served by relatively unimportant characters in Macbeth?
Shakespeare's plays rely heavily on dialogue because it is difficult to represent much action on a small stage. This is true of almost all stage plays, in contrast to motion pictures which can show all kinds of action, including enormous battle scenes and space travel. Shakespeare characteristically used minor characters to convey information to the audience about events that were taking place offstage. A typical example is found in Act 5, Scene 2, in which the minor characters of Menteith, Caithness, Angus, and Lennox engage in a conversation which is loaded with information for the audience. The very first words, spoken by Menteith, tell the audience:
The English power is near, led on by Malcolm,
His uncle Siward, and the good Macduff.
Then Caithness supplies information about what is going on at Dunsinane:
Great Dunsinane he strongly fortifies.
Some say he's mad; others that lesser hate him
Do call it valiant fury.
And Angus goes so far as to describe what Macbeth is thinking and feeling:
Now does he feel
His secret murders sticking on his hands.
By the time these warriors have concluded their brief conference, the audience is brought up to date about everythiing. Lennox speaks the final words:
Make we our march towards Birnam.
In most of Shakespeare's plays minor characters will be seen either bringing news to major characters about offstage events or conversing with one another about such events. This is particularly obvious in Macbeth, King Lear, Julius Caesar, and Anthony and Cleopatra.