Was your home built between the mid 1960s and late 1970s? If so, it may have aluminum wiring.
Aluminum wiring isn’t a hazard in itself, but when receptacles, conductors, switches, etc. not intended for use with aluminum wiring are installed, the threat of a hazard is possible. Why? Aluminum has a much higher rate of thermal expansion than the connection on the switch or receptacle, which makes it possible for it to expand and deform. This can lead to a loose connection and, under the right electrical load conditions, could cause sparking, overheating, or even a fire.
Aluminum wiring should be evaluated by a qualified electrician who is experienced in evaluating and correcting aluminum wiring problems. Not all licensed electricians are properly trained to deal with defective aluminum wiring.