Symbolism, Imagery, Allegory
If there's one thing we know from ancient Greek mythology, it's that doing good deeds can win you major brownie points with the gods. And the story of King Midas is no exception. Dionysus grants Midas's wish because Midas has done him a favor. In that sense, the wine god symbolizes the power and potential kindness of the gods. Basically, if we're nice, we might get a prize.
The prizes continue after Midas's wish goes down the pooper. When Midas begs for help, Dionysus is there to be sure he doesn't turn any more Pop Tarts into gold. Now we get a new lesson: acknowledging your mistakes is the way to go.
To recap: Dionysus both gives rewards for good stuff and saves people from their mistakes. Sound like any modern religions?