If your guide pins are stuck, the caliper won't be able to slide properly.
With a sliding caliper, when you apply the brake, the piston pushes one pad against the disc (rotor), and simultaneously pushes back against the caliper (Newton's equal and opposite reactions), causing the caliper to slide along the guide pins, and pull the other pad against the disc. If the caliper cannot slide, the second pad remains forced against the disc, and you're effectively driving with half the brakes on on that wheel, hence why it gets hot. You'll find that if you jack up the the car, that wheel is much harder to turn than the other side.
Remove the caliper, and both guide pins. Clean them up until they both slide freely, re-grease and reassemble, using new gaiters if the old ones are damaged (which is quite likely, as that's the usual reason for them siezing). Do the same on the other side so that you know both calipers are in the same condition.