Yes! The goal of wearing stackable rings is to be able to express yourself freely without any strict, unreasonable rules. You can mix any metals, from 14k gold and gold-plated silver to sterling silver rings in one stack.
However, stacking rings works best when it’s intentional instead of randomly stacked with no particular meaning. Even if you’re mixing metals, make sure your selection of rings matches the vibe you’d like to achieve, like stackable rings for summer, romantic dinner night, or casual holiday getaway.