installing a new ceiling fixture
I am replacing a new bathroom ceiling light fixture. I removed the old light fixture and it was attached to the wall with only a black to black wire and white to white wire. There was no ground wire, but there was a green screw on the plate. the electrical box is plastic and not metal and i noticed a thick copper wire that was curled up in the wall.
My question is, the new light fixture has 3 wires: black, white and bare copper. Do I attach the black to the black, white to the white and copper to the thick copper wire in the wall or the green ground screw or to nothing at all. I didn't attach it to anything and the light works fine. Should the copper wire from the light fixture be attached? what's the danger of not grounding it?