What is a typical light bulb screw temperature? Is it safe to put a microcontroller there?
Wikipedia:
"The glass bulb of a general service lamp can reach temperatures between 200 and 260 °C (392 and 500 °F). Lamps intended for high power operation or used for heating purposes will have envelopes made of hard glass or fused quartz."

Assuming the glass reach those temperature ranges, the metal should be near that too.