Shader data for a texture is handled through plain text. The game's TPC format combines the texture and shader data into a single file, though you can also have the shader as a separate file (TXI format).
The game has various shader semantics, but it sounds like the sort of thing you want is an environment map (aka cube map). These are separate textures that get projected onto the model, depending on the viewing angle, for effects such as glowing and metal. I've attached an example TXI file, though it just looks like this:
envmaptexture CM_Baremetal
envmaptexture means use an environment map texture, and CM_Baremetal is one such texture. It's that simple.
The game has various other cube maps in addition to CM_Baremetal, such as CM_Bright (blue/green glow), CM_SpecMap (wet), and mycube (HK-47's shiny plating). It's also possible to make new ones, and I believe there are some mod resources on this site that have more.
The intensity of the shader is determined by the texture's alpha channel (more black = more shader).
Note that you can only have one shader per texture. You cannot, for example, have a texture with parts that are metal and parts that transparent, as there is only one alpha channel for them to use.
N_Mandalorian01.txi