Quick take
Test iron, manganese, copper and pH before choosing treatment. Source-water iron points toward well-water filtration; copper plus low pH points toward corrosion control.
Iron and manganese
These well-water minerals can affect taste and create visible staining. Oxidation/filtration is a common whole-house path.
Copper and corrosive water
Low-pH water can dissolve metals from plumbing. In that case, neutralizing the water is more important than simply filtering the taste.
Point-of-use treatment
For drinking water only, certified carbon or RO can reduce selected metals, but source-level corrosion problems should still be fixed upstream.
Use testing to choose
A broad tap-water or well-water panel can distinguish source chemistry from plumbing-related contamination.