What would cause a grinding noise when you only turn slightly to the left on a 1996 Geo Metro?

If the "grinding noise" is present while cornering left and all but disappears when cornering right, my experience* says it's your right rear wheel bearings needing replaced.

* My '96 did the exact same thing

another thing to check is my exhaust pipe would rub the rear suspension on the passengers side and make an awful noise only when turning left and it would be worse with more weight in the car