When should I ovulate on metformin? I do not have dietbites a bit overweight my doctor prescribe them to me because I grow facial hair.

Not consistent. Spontaneous menses occur in about 4-6 weeks in most patients. It takes a while to build up to a high enough dose to see some effect. I find that most need to be at least on 500mg twice a day and some need 1000mg twice a day. Ovulation may start a few months later. However, ovulation does not always occur on metformin alone. Adding Clomid (clomiphene) to the metformin may make ovulation more consistent.
It's not that simple. If a woman in the fertile age range is overweight, has increased facial or body hair, irregular periods, and some acne; then her doctor can check her hormone levels to see if she has pcos. Treatment for pcos tries to normalized hormone levels, which should decrease her symptoms (which were due to hormone imbalances), and allow her female hormones to cycle properly. Hard to guess when that will be.