Recap: Silenus is a satyr, a chubby dude with goat legs and horns. These guys often play the pipes and like to chase nymphs. Silenus is also a friend and teacher to the god of wine, Dionysus. In this story, Silenus is traveling with Dionysus when he gets stupidly drunk and loses his way. A group of peasants escort the satyr to King Midas. Midas throws Silenus a party before helping him locate Dionysus, and Dionysus rewards Midas for returning Silenus in good health.
As a character, Silenus is what scholars would call comic relief. That means he's the funny guy. His job in the story is do stupid things that make the audience laugh. And on the whole, he's pretty good at it—especially if you follow the version of the story where he gets smashed and passes out in Midas's garden. And to be clear, we're laughing at him, not with him.
As Dionysus's teacher, Silenus represents everything that's important to the wine god. Silenus loves music, wine, women, and having fun. In fact, he loves these things too much—this guy is always drunk and always getting into trouble. (In another myth about the satyr, Silenus is captured by a pair of shepherds and made to tell funny stories. You see how he is?)
Bottom line: Silenus is all about excess. He shows us what happens when you have too much of anything. In this way, Silenus is actually a perfect addition to the story of King Midas. A little wine might be good (for the 21 and over crowd), but too much is bad. Same with gold, it seems.
Through his role in this and other myths, Silenus has become a mythological poster boy for debauchery. Want to see him in action? Check out these sources:
P.S. If you want to learn more about Silenus, take a look at Shmoop's guide to the Satyrs.