Please be aware that different metals react and change due to environmental elements. Sterling Silver will tarnish over time. The best way to keep it from tarnishing over time, besides wearing it, is to store it in a box or an air tight bag.
Gold plated items are coated in a way that will eventually wear off. The best way to avoid your plating coming off is to avoid getting chemicals on it which include perfume, lotions, hair products, etc.
Brass and Bronze tend to oxidize and tarnish more easily than precious metals from everyday wear, but the patina of the metal aging is also very beautiful.
Enamel is glass fused to metal, so if it is dropped on a marble or tile floor, there is a good chance it might chip. Please take care to not have it cluttered with your other precious jewelry, but most of all remember that it can be repaired, so enjoy it!