The wyrd's attentions are drawn to Macbeth as they look into the future, and they waste little time meeting him on the heath. They appear to Macbeth and tell him that he will first become Thane of Cawdor, and beyond that he will become King. Now this is certainly perceived as good tidings to Macbeth, but the wyrds leave Macbeth with a somewhat cryptic remark that there may be a price to be paid. The price is that although he will be in happy circumstances, Macbeth will, in reality, be unhappy. Macbeth's comrade Banquo, although his circumstances will be less happy, will be happier.
Within that single scene is so much mind-twisting, thanks to the aptly named "wyrds", that it takes the rest of the play for the audience to unscramble it; but the prediction does turn out to be true. When Macbeth's ambition to be King drives him to murder King Duncan, his guilty conscience drives him insane. "O, full of scorpions is my mind," Macbeth laments. Yet Banquo, who is later murdered by Macbeth's agents, has piece of mind and is free from guilt. "Happy is unhappy, and unhappy is happy," were the words of the wryd.
At the time of the prophecy, Macbeth appears to be, and is, a loyal and faithful general to King Duncan and a brave and honorable man. For Macbeth to kill King Duncan in his sleep is the apex of contemptable behavior, ie., "Fair is foul". These two incidents are two clear and parallel