When choosing a 3D printer, a good place to start is understanding the material you want to use to create objects. At its most basic, you'll need to choose between producing plastic or metal objects. 3D full metal object fabrication will place you in a high-cost category and reduce your choices considerably.
Plastic opens up your options wide. There are plastic filaments that embed metallic flecks or wooden fibers, allowing you to 3D print objects that have metallic or wooden characteristics but are still fundamentally made of plastic. The metallic objects can rust, be shined up, or be ferrous enough to attract a magnet. The wooden objects can support wood stains and finishes.
Almost all of the FDM (fused deposition modeling) filament printers we've proposed above will print a wide variety of plastic filaments. In addition to the wood fiber and metallic filaments, you can print carbon fiber, nylon, ABS plastic, flexible plastics, and more.
Generally speaking, the more exotic the filament, the hotter the hot end (the part that melts the plastic) will need to get. Look at the material specs for the filaments you want and compare them to the max temperatures of the hot ends. Generally, if a printer says it supports multiple filament types, you're good. If a printer only supports PLA or does not have a heated bed, you're limited to a more simple plastic.
FIlament printers have a range of key features that you will want to consider. Heated beds allow for better object adherence while printing, but large heated beds on open-framed printers will dissipate the heat at the edges, reducing the reliability of those prints.
Some filament printers have auto-alignment, which sets the distance between the bed and the print head. Personally, I hate aligning printers by hand, so I always look for the automatic alignment feature. It's usually on the more costly printers, but it's worth it.
Some filament printers support multiple filaments. This can be useful both for printing multiple colors or for mixing filament types, like printing a flexible hinge between two rigid hard plastic elements or printing supports in a dissolvable filament, making it easier to create a finished object. We even spotlight a filament printer that comes with a CMYK ink cartridge and it sprays ink on every layer to impart full color.
If you want to create highly-detailed objects for miniatures or jewelry, you'll want to look at a resin printer. These use light to harden plastic resin in thin layers. They're messy, but their detail is often second to none.