In this scene, Macbeth deludes himself into thinking that he has control over his future. After his encounter with Banquo's ghost, and his fear, anxiety and panic at seeing this apparition, he decides to consult the witches about how to protect his crown.
Macbeth seems to believe that he can continue to murder people and that no one will notice. He is further deluded by the idea that holding on to the crown is his only problem. What good is a crown when everyone suspects that you have murdered your way onto the throne, that you have killed again, and will do so to protect your crown. His life will be dominated by thwarting threats, what is he going to do, kill everyone!
What kind of King is Macbeth, clearly a tyrant, not a good king. Kingship is about selfless devotion to country in the absence of self-interest. Macbeth is all about self interest, and power.
This is the scene where Macbeth sees Banquo's ghost at the banquet. Macbeth is the only one who sees the ghost and he is naturally very shaken when he sees it sitting in his seat at the banquet table. The ghost apparently shakes its head at Macbeth because he says to it, "Never shake / thy gory locks at me." When the ghost disappears then Macbeth swears to his wife that he indeed saw the ghost and he goes on to say that at one time when a man was dead, that was the end of it. He calms himself telling the bewildered guests that he has an infirmity that is no big deal and he occasionally acts oddly, but they should proceed with the banquet. When the ghost reappears, that ends the banquet as Lady Macbeth sends the guests home. Later Macbeth says he will speak to the witches the next day so that he can find out more about his future and that being forewarned is all that he'll need to thwart any evil that may be in store for him. It is in this way that he is deluding himself. He does not remember what Banquo said shortly after the two of them encountered the witches the first time: that sometimes evil beings will lead them astray by giving them little bits of truth and big promises. The witches will make Macbeth feel secure by giving him tiny bits of truth but actually miseading him.