entity_basic is a legacy shader, it is for entities that use the old Diffuse, Normal, Specular system. Metalness is a PBR texture it will not work with that shader, you have to use the apbr_basic for PBR textures.
Not sure why you can't use the apbr_basic texture, you don't have to do anything with it just have the name of the Shader in the entities FPE file and then use the correct naming on the textures and it works.
For metal it's not just a the metalness that makes it look shiny, you also use a _gloss texture, which is actually a _roughness texture named _gloss, it's a grey scale texture with pure white being 100% rough and black being 100% glossy.
i7 7700,k NV1070 8GB, 16GB 3200mhz memory, 1x 2TB Hybrid, Win10.
i5 4760k, NV960 2GB, 16GB 2333mhz memory, 1x 2TB Hybrid, Win10.
i5, NV1050 4GB, 8GB memory, 1x 1TB HDD, Win10.
i3, Intel 4000 series graphics, 6GB memory, 1x 500gb HDD, Win8.1.