Explain the Gyges and King Candaules story? Why does Dunstan tell this Story?

Dunstan tells Boy the story of King Candaules, who was so proud of his wife’s beauty that he asked his friend Gyges to look upon her naked. In one version, the queen ends up falling in love with Gyges and they steal the throne from the king. In the other story, Gyges kills Candaules.

In telling the story, Dunstan compares himself to Gyges. In reality, however, he is nothing like Gyges. Gyges responds to the event directly, whereas, Dunstan responds to his situation by telling a story.