Romex (which I'm guessing was used in your installation) carries a
ground wire. (Well, halfway recent Romex does...) Often at the switch
end of the cable there's nothing to attach this ground to. A thoughtful
electrician will at least leave it in place at that end, and ground it
at the other, so that future components have an available ground. This
is not a problem at all.

If your replacement switch has a ground terminal, use this wire to
ground it, but first I'd check to make sure it's connected to ground (at
the other end of the cable).

photoflavor wrote:
Greetings. I bought a dimmer switch to replace the standard light
switch in my kitchen. I identified that it needed to be a 3 way
switch since there are multiple locations to turn these lights on/
off. When I removed the current switch, I noticed that the bare
copper ground coming out of the wall isn't connected to anything -
it's just covered in a plaster-esque substance. Is this a hazard?
Should I be concerned? If this is a problem, would it simply trip the
breaker, or should I be worried about a fire?

Thanks!
Zac