One name covers a range
"Nylon" names a broad family of engineering polymers, and "metal" is broader still. Within one name, different grades can differ substantially in stiffness, toughness, temperature behaviour and dimensional stability. Naming only the material leaves the selection work to whoever comes next.
That is why our materials page lists dimensions of assessment — stiffness, toughness, temperature, dimensional fit — rather than a catalogue of materials.
What to ask instead
Swap the material question for an operating-condition question and the information content jumps: what does this part have to withstand? In which direction is the load? Roughly what temperature range? Will it sit in contact with chemicals or UV for long periods? How often is it removed once installed?
These questions need no specialist background to answer, yet they narrow the options to a few directions.
Different processes demand different things of a material
Metal additive manufacturing is confirmed against alloy, machining, heat treatment and inspection requirements. Ceramics and specialist materials start with a manufacturability review for the specific conditions, with material properties, geometry limits and inspection criteria agreed before the project starts.
Material and process cannot be decided separately. Fixing the material first and looking for a process afterwards tends to mean rework.
One exception: being unsure about material is a reason to talk, not to wait
Being unsure about material does not hold anything up. As long as the application and operating conditions are clear, choosing the material is something we can work out together. What actually slows a project down is a locked material name with no clear application behind it.
So our suggestion is simple: describe what the part must do first, and leave the material to be settled together during assessment.