in addition to the programs the other Sebastian mentioned, there are some tools for metal additive manufacturing.
The most popular one is in my opinion Magics (https://www.materialise.com/de/software/magics), which can be used to generate machine code for almost every SLM and SLS plant.
Most printers, like Ultimater (Cura), Prusa (PrusaSlicer), or Raise3D (Ideamaker) offer software for g-code generation.
In my opinion, the most powerful for Materialextrusion is by far simplify3D.
There are several additive manufacturing techniques and several machines. Almost always, a manufacturer has its own program for its machine.
There are programs to develop 3D digital models, programs to triangulate (tessellate) 3D digital models, and even those that transform 3D models into slices that can be made for 3D printing into the material you need.