Due to the gravity being almost 1/3 Earth gravity, the inhabitants have become significantly weaker since they don't need to use much strength to move. Should someone from another planet come to Mercury, and walk "normally" it would seem like they were able to fly since they could jump so high.
The supreme temperature difference from the being on one side of the planet versus the other, causes most of the people live in the place in between, in moving cities. They are forever moving in order to stay in the gray zone where the temperature is livable. Even though the cities move to protected areas, the people here have developed a resilience to heat changes. And their Mechs are able to move in both extreme heat and extreme cold.
Iron is the main source of income for the people of Mercury, as it is plentiful and easy to mine. It is a small planet, so they have explored the entire planet, finding quickly the best places to mine. Due to the moving cities, they have precious little time to mine at certain spots before it gets to a temperature that the humans couldn't stand. So they are quick and diligent with their work.
