If it is not a mech mod....then it is regulated or a stick battery. All stick batteries are made from stainless or plated brass with an anodised or painted finish. Regulated mods will be stainless, aluminum, plastic. As for SOLID brass or copper....you will only find that in a tube mech mod.
In order to help you with the people here and at the shops.......a "mod" has removable and rechargeable batteries....or a battery pack that can be charged in the device. Beyond that...it is a "stick battery" like an Evod, Vision Spinner, eGo Twist, etc.