The most common metals which cause problems for your pool are: copper, iron, and manganese.
Copper
Copper may cause your water to discolor, though it may still appear clear. If you have copper present in your water you can remove it by adding a metal sequestering agent such as SeaKlear. It is important to locate the source of the copper so the problem isn’t constantly reoccurring.
Iron
Iron is often introduced to water via your source water which is why it
is important to choose good fill water. FerriIron tablets can help this issue.
Manganese
Manganese is a mineral and is often introduced to your pool via your source water, the same as iron. Super chlorinating or shocking your pool may oxidize manganese out of the water. This would allow the metals to settle on the bottom of the pool so you can then vacuum it up with your pool vacuum. SeaKlear is a product we recommend at Ask the Pool Guy to remove trace amounts of manganese from your pool water.
Need some one tips on cleaning up metal stains from your pool surfaces? Check out some info here.