At the risk of being flagged "not an answer" I am going to ignore your overly-broad and perhaps-unsupported worries of "chemicals and metals" and concentrate on pathogens.
While it may seem impossible, devices exist that use batteries (you can charge them typically with any USB charger) and that remove pathogens - bacteria, viruses, protozoa, etc - without heating the water or leaving a taste. They operate on UV light, which is a great sterilizer. One manufacturer sells a number of models that can easily fit in a pocket, for less than $100. My only affiliation is that I bought a different model from that manufacturer and am very happy with it. I used it throughout the Pacific, in places where the hotel told us to treat the water (boil for 20 minutes, one place said), and never had any water-related issues. A family member took it through Asia and stayed healthy in places where the water was known to be untrustworthy. You can easily use it for days on a charge, it's not plugged in while you use it, and there's no concerns about power adapters or the like since it's just USB.
You treat about 500ml of water at a time - a mug or glass - and it takes 90 seconds. I wouldn't want to treat a bathtub, but for the volumes you're likely to drink it's fine. It's so small you can take it into a restaurant and treat the tap water they serve you. It's easy and it works.