What would the monthly insurance rates be for a twenty-five year old driving a Grand Am?

That would depend on many factors, such as the year of the car, make of the car (engine in car), your driving record, how long you have had your license, how much you drive your car, what state/province you are in etc. If you have been driving for awhile and have a clean driving record, then I think it should be under $100 / month.

Your best bet would be to get a online quote from the site below in related links.