It is not uncommon to find metals, often called free metals, dissolved in pool water. Usually they come from source water, sometimes they come as a result of the erosion of metal pool fixtures, such as heater cores.
Free metals in pool water can cause staining of pool surfaces and inhibit the performance of water sanitizers. Ideally, there should be no metals in the water: 0 ppm. If metals are detected in your water you will need a sequestering agent to render them harmless.