Based on what I've read, joining a fraternal or secret society will open the doors to a world you didn't know existed that goes back centuries in which you'll learn about arcane Eastern mysticism, where the Templars hid their riches from the Crusades, how the Rosicrucians used alchemy to transmute base metals into gold, the way the Illuminati secretly controls the world's governments, and how your organization is an essential part of those traditions. Umberto Eco will even write international historical thrillers about your membership.
On the other hand, it may just be potluck dinners every other Tuesday and a lot of drinking. Depending on your preferences, one of these scenarios is probably a lot cooler than the other one, but only you'll know the answer to that.