From your description I would assume that to be the power steering pump slipping on the drive belt. You could check the tension if you want, otherwise just don't turn the wheel so hard.
Turning the steering wheel farthest left or right for a few seconds will cause a loud squealing.
The cause of the squealing sound is because you are turning the steering wheel completely to the right or left
A loose or worn belt. Also check the power steering fluid.
Could be a worn belt, failing power steering pump or low power steering fluid.
The steering wheel will be harder to turn. First sign is squealing when turning, but why don't you open the hood, unscrew the cap on the steering pump, and look.
squeeling when turning, generally means your power steering fluid is low. check steering fluid
Power Steering pump my have a leak...
if the pump has failed completely it will cause stiff turning, obviously not being assisted by power. if the pump is failing there may be a squealing sound when turned in either direction. This is not to be confused with the squealing made when turning the wheel to its limits.
loose fan belt, or low power steering fluid. Depending on the sound, it could also be the brake pad wear indicator.
A Geo Metro is a front wheel drive vehicle. When a squealing noise occurs when the wheel is turning, it can be an indication of damage to the CV joints.
It may need just a simple belt replacement. If you change one, change them all.
A loose steering belt could be the problem and so could worn out pump bearings. You could go to the Internet and type in buzzle.com Hope this helped.the website will tell you how to check your car and help guide you.