Most likely you have no lining left on your brakepads and they need to be replaced as well as the rotors. There is also a chance your backing plate is rubbing on the rotor. Check for gouges in the rotor with a flashlight to verify any obvious damage.
The scraping sound coming at the time of braking is due to the friction between two metals. when braking some components might be coming near and contact each other which can cause this sound.
Could be a small rock or other object stuck between the brake pad and the rotor. If there's no debris there, part of the caliper or pad may be missing or misaligned.