Lightswitch Problem

My headlights aren't comming on. When I pull the switch out to turn the lights on I hear a click kinda like a relay pulling in and when I push the switch in I here another click like a relay dropping out. I looked under the dash and there is a small silver box , i'm thinking relay, piggybacked on the switch itself. It has a few heavy guage wires connected to it. It got dark on me last night before I could put my meter on it. I didn't find anything on it in my FSM.
What is this relay thing?

 

Wouldn't there be some kinda reset on it, then?

 

Thanks Bill.
It's like an overload relay I guess.
Pulling it out fast didn't work. If I leave the switch on the overload trips in about 2 secs then trys to reset after awhile but trips again right away. I did a quick wireing check and cleaned and tightened grounds.
What are the chances of it being a bad overload?

 

spose it could be... I've seen circuit breakers rated for 50 amps pop with a 10 amp load