To be effective, an opening scene must accomplish a variety of purposes. What different functions are served by Act I scene 1 of Macbeth?

There is something about this opening scene that gives the
play its overall tone of menacing evil. The way that the witches chant together, almost
as if there words were an incantation and they were casting a spell, immediately plunges
us into the world of evil and witches. We also need to be aware of the dramatic impact
of such a scene on an audience. It is very easy to dismiss such aspects because we study
plays like this rather than trying to visualise what they would look like. However, let
us imagine we are in the audience, watching this opening scene. Depending on how the
director chooses to play it, the opening scene is likely to involve darkness, thunder
and a storm, dramatically introducing the witches but also casting a shadow over the
rest of the play. Note too, the words of the witches and the way that they seem to
represent chaos through the paradoxes of their speech. They refer to a time "when the
battle is lost and one" and "Fair is foul, and foul is fair," indicating the way that
they represent an anarchic state that overturns the normal order of things. Starting
this play in such a fashion clearly emphasises the role of evil in the play and also
highlights the importance of the witches in Macbeth's downfall.