Yes, if there is enough metal in the water it will tend to deposit on the surface of the pool, ie cause stains. If you have metals in the water you can prevent staining by adding a sequestering agent. If you are filling the pool with well water it is a good idea to get your water tested beforehand. That way you can know if you need to have an appropriate sequestering agent on hand when you fill the pool, or make arraingments to have water trucked in. Municipal tap water very rarely has a metals problem and your water company should be able to tell you if there is an issue, most have such things listed at their web site.
I have a fiberglass pool also. You can get metal from new water, some chemicals. even the wind blowing in junk. What I do is add Metal Magic By pro team every week (3 oz) This has kept me in good shape. keep your water balanced brush and vacuum and you will find fiberglass is easy to take care of. I would suggest you purchase a good test kit dont even consider test strips you have probably read they are not accurate I tested them they are not even close. After you get every thing going and get comfortable with your pool start reading about the addition of borax this is a great addition to your pool water.
ric is right, you can get metals staining in fiberglass pools from many sources, not just fill water. Fiberglass just tends to stain easily. You can manage it just as ric says - with a sequestering agent. I would just balance your new water, and if you notice any stains, you can then lower your ph to 7 and put in a sequestering agent. You will then have to always add your matainence dose, especially when adding new water. Don't worry it isn't hard, and getting rid of stains if you get them isn't hard either!