By 3D metal models, I mean the ones that come in kits from Piececool and Metal Earth. The models are generally very small, and consist of many small pieces that get cut out of thin metal sheets and attached together by twisting pieces with tabs into pieces with holes.
I mainly do the ones from Piececool, as they are bigger, more intricate, and (at least in the past) more colorful.
This hobby is good for people who like model building. It is specifically good for people who like the model building aspect of formats like Lego but want something that is cheaper, more detailed, and takes up less space.
The absolutely required tools are a flat needle nose plier and a clipper. The clipper is required to cleanly cut out the pieces from the metal sheets, and the needle nose plier is required to twist the small tabs.
The optional tools are a cylinder shaping tool set or mandrel for shaping small tube structures.
Metal Earth has previously done a lot of famous landmark sets. They also do a lot of vehicles, including military, cars, trucks, helicopter, planes, ships, trains, and tanks, and space themed sets. There are also other things like musical instrument models, dinosaurs, armor, guns. Recently they have been partnering with a lot of IPs like Star Wars, Marvel, Western Star, etc. to create themed models.
Piececool has a lot of Chinese culture inspired models, like architecture, suspended palaces, hanging jewelery, cranes, armor. They have large military models, including large battleships that have mini planes on then. They also carry the famous landmarks, vehicle, and everyday objects models that Metal Earth has.
Some interesting models that Piececool has in particular are their extra large ships, The Wind Breaker and Nine Heavens, and their more detailed versions of The Queen Anne’s Revenge and The Flying Dutchman. They also have a large train front car Mogul Locomotive. I think their Chinese parade car and Bridal Sedan are very colorful and interesting. Piececool’s version of the Notre Dame is larger and fully colored, it is very beautiful and they discount it to attract people who are new to the hobby.