Exterior light fixture

The bare copper wires are your ground wires. They don't need to be connected to the box because it's non metal. The grounds are all crimped together in the box as they should be. Once you replace the broken switch, the ground wire in the box should be attached to the green screw on the switch. At the fixture location, the bare copper ground needs to be attached to the fixture ground wire with a wire nut. If the fixture box is metal, then the ground wire needs to be attached to it. Any bracket needed to mount the fixture should also be connected to the ground.