Defold is primarily meant for 2D dev in that most of the productivity tools it has were made with 2D gamedev in mind (so far) but the point still stands that it is actually a 3D engine.
Check out this example for a very simple base for a first person shooter https://github.com/subsoap/fps
I have some 3D materials here DefMaterial - A Collection of 2D + 3D Materials
Although the built in model material stuff has changed since then so if you are making something for production you’ll want to study those and make any necessary changes.