2003 Hyundai Elantra making grinding noises?

just because you have meat on your pads doesn't mean that the brakes arent grinding. If you have a bad caliper in the front, it means the breaks arent releasing all the way and there is constant friction between the pads and the rotor. The same could be happening with the drum breaks in the rear. If a break shoe is hanging up and nort releasing all the way, it could be making a grinding noise occasionally, especially after it rains and grit is thrown up between the drum and shoes. Get a real mechanic to check them, but not someone who is going to sell u something u dont need. ask around for a trustworthy mechanic or live with the noise.