How do I change light bulb in flush mounted fixture?
It turns out that the previous owner had 3 100 watt bulbs in a fixture only rated for 60 watt bulbs. This caused the paint on the metal to peel/adhere to the glass. It eventually fell off on its own since I left the bottom screw off. 

One of the sockets was blackened from the heat, so all 3 of these things in my house are getting replaced ASAP.