The first act sees an introduction to most characters, including the Witches who it opens on. Banquo and Macbeth return from war and are seen as war heroes (Macbeth in particular). The witches make their first set of predictions which deceive Macbeth but not Banquo. After their prediction that Macbeth would be King, Lady Macbeth convinces Macbeth to kill King Duncan.
For more information download the Macbeth Act One Overview
If you feel ready to test yourself on Act One, complete the following questions. You can find the answers in the revision section of the course.