The plastic injection molding process is arguably the most common process in product manufacturing in the current age by volume of parts. Properties of plastics now make them suitable for things you wouldn’t have even imagined possible just a few decades ago. Injection molding quickly and inexpensively shapes these plastics into useful parts.
Creating extrusions is a process where soft(ish) materials are confined within a space, then that space is shrunk while leaving only a small opening for the material to escape
Thermoforming is the process of taking a flat plastic sheet, heating it, then using pressure to form it around mold so that it's no longer flat, but a complex 3D shape.
Sheet metal undergoes many different stages, including the process stage, and the building stage which consists of cutting, forming, welding, and assembly.