It will do nothing to change their temperament other than to reduce their sex drive. So your male will be less likely to fight over females, wander, mark his territory and mount.
That being said, he still might do these things anyway.
If your male is already aggressive, it will do nothing to stop the behaviour. If your male is happy-go-lucky, he still will be after the surgery.
However, it's best to wait until your dog has finished growing to his full height, as early neutering will stunt his growth and he may look more like a female.