Abs break pads and rotors
First things first, you may have been told to replace your break pads every year but you didn't listen. Now your hearing a "metal scrapping metal" sound every time you hit the breaks. That's your rotor scarping against the metal break disc because your break pad wore through. Go change you break pads and have your mechanic double check that your rotor is isn't damaged.
Check your break fluid
Are you hearing a squeaking when you hit the breaks? does your stop on a dime ABS breaks now stop in about a foot or so? You probably need break fluid. You should check your break fluid every time you check your oil, it's that important for your safety.
Check for damage underneath the vehicle
One of the benefits of anti lock breaks is the speed sensor that predicts when the wheels will lock up and prevents it. However the gap between the tone wheel and the speed sensor is an area where foreign objects can get stuck and damage communication between the speed sensor and the breaks.
Clean the ABS computer
If your experiencing the ABS light coming on for no particular reason this could be a malfunction of the computer. Pop up the hood and pull out your vehicle's manual to locate the ABS computer. Look over the wires around the computer for any dirt, disconnections, kinks or exposed wires. You local auto parts store should sell cleaner specifically for ABS computers.