You were all psyched up for a quick tire rotation—until you found a rusted-on wheel. Here's how to “unstick” a wheel and prevent it from sticking again.
You'll need an 18-in. length of 2x2, a can of spray rust penetrant and a hand maul. Jack up the car, support it with jack stands and remove the lug nuts. Spray the rust penetrant generously into each mounting hole. Let it sit for five minutes, then rotate the tire a half turn and repeat the application. Screw one lug nut onto a stud a few turns to prevent the tire from flying off once it's free. Place the end of the 2x2 on the outer edge of the wheel and smack the wood with the maul, just enough to create some breaking force and vibration. Rotate the tire a quarter turn and repeat the smack/rotate procedure until the wheel is free.
Clean the mounting surface on the brake drum/rotor or hub with a wire brush. Then coat the surface (never the studs) with a light coat of anti-seize lubricant.