When installing a new light fixture in an old house or an old metal light fixture in a new one, you may encounter a problem: there is no way to ground the fixture. The problem can be easily solved in either case. If the house has outdated, two-strand wiring, you can run a separate ground wire to a cold-water pipe or to an outside ground rod and connect it to the fixture ground wire. If the fixture does not have a ground wire, you can drill a hole on the casing, install a ground screw and attach the ground wire to that.
Run a length of 12-gauge ground wire through the attic space from the fixture to the nearest cold-water copper pipe.
Using a screwdriver, attach a grounding clamp to the pipe and connect the wire to the clamp.
Run the ground wire to a location outside the house where you can pound in a metal ground rod if the house has plastic water pipes. Pound the rod 8 feet into the ground and attach the ground wire to it with a grounding clamp.
Connect the other end of the ground wire to the ground wire on the light fixture and install the fixture as you normally would, connecting the black wires and the white wires and screwing the fixture into place on the electrical box.
Drill a hole somewhere on the metal casing of the fixture large enough to screw in a ground screw.
Screw the ground screw onto the inside of the casing.
Make a clockwise hook in the end of the ground wire with pliers and hook it around the ground screw. Tighten the screw well with a screwdriver, then connect the rest of the wires and attach the fixture to the electrical box.
Don't forget to attach the ground wire to the ground screw on the electrical box as well, if it is metal. Ground rods must be made of a conductive metal and have no paint or other non-conducting material on them. You can use this ground rod to ground other fixtures in the house, but rather than running a bunch of separate ground wires, you may want to consider updating your house wiring.
Make sure the power is off to the fixture before you make any connections. If you are not sure, test the leads with a voltage tester. Failure to ground metal light fixtures is dangerous and could result in an electric shock for anyone touching them.