the brake pedal has a rubbing squeak sound
on 2006 Ford Five Hundred

When I push on the brake pedal, I hear a sound,

2 answers
Your brake pads have a metal scraper on them and when the brake pads get low they start scraping when brakes are applied to warn you your brake pads are worn out. There is a slight possibility that you have a ridge on your brake rotor and they need to be machined.
get your brakes checked as it may be the warners telling you the brakes are low and need to be replaced.