Brakes noise

I own a 99 1/2 TON Silverado Pick Up

30,000 miles. The breaks squeak when applied. What is the cure?

A brake job. The squeal is probably the indicators telling you the brake pads are worn, and need replacement.

Likely it is just trying to tell you it is time for a brake job.

Took the vehicle to a break shop. After he inspected the brakes, his comment" How did you drive this truck 30,000 miles without hitting the brakes.
The rotors were glazed over, causing the noise. He sprayed them with acetone. Many thanks for the comments. Bob Holt