I have 1993 sts the calipers are sticking. Is it the calipers or the master cylinder? Any ideas?

Not nearly enough information.

Could be either as well as guide pins not lubricated. The caliper slides on the pins that hold it on to the spindle. With the wheel off, wedge a large screw driver between the inboard pad and rotor and force the pad into the caliper. Once retracted, you should be able to easily slide the caliper back and forth on the guide pins. If not, remove each pin one at a time and lube with silcone brake grease. If still binding, I would suspect the brake hoses going to the caliper. They can deteriorate internally, effectively blocking fluid flow back to the master once the pedal is released.

It's probably the caliper piston sticking. The hydraulic system gets "sludge" in it and the piston sticks in the bore. I clean them every brake job. I used to replace the seals but have been having a hard time getting the cheap kits lately so the last 2 times I reused the seals and they've been fine.

If you take the calipers apart you can use air pressure to blow the piston out of the caliper. You have to use a piece of wood to stop it so you don't damage it because it will get blown out hard. Clean the caliper and piston with brake cleaner or alcohol only. Remove the seals first (carefully if you think you'll reuse them). Reassembly isn't that hard and you can wiggle the piston back in by hand but it may take several attempts.

Bleed the brakes until you get clear brake fluid out and no bubbles.

Clean the guide pins and the contact points where the caliper slides.

Not knowing your level of mechanical ability, using the screwdriver to retract the caliper piston will help determine if, in fact, the piston is the culprit. While I agree it could be a binding piston in the caliper, thats probably 3rd on the list of possibilities. My 84 Eldo has the original calipers and gets bled and or topped off with new fluid only when pads are replaced. I would think caliper failure is more common in the snow belt rather than here in California? If you're not up to this series of diagnostics, then print them for the mechanic who does ck it.

Work your way into it. My first guess would be the pins, common problem. Follow carnut's advice before getting into the caliper proper. If that doesn't do it do as zonie says. K_C