When I had a 500 credit score I tried to get a car loan but couldn't get the car loan unless I had a cosigner sign the car loan agreement along with me.
The cosigner had to have at least a 700 credit score before I got approved for the car loan.
So unless you get lucky and find some used car dealership that approves bad credit then you'll have a hard time getting approved for a car loan especially a new car loan with a credit score of 500 which is not good.
You may be able to get approved for the car loan with a 500 credit score if you can find a cosigner that has a good credit score and have them sign the car loan agreement along with you.