Little information. If in Garry's Mod on my maps, and possibly any others, you see a model that is somehow inadequately lit (most often these are doors or various dynamic models), then check what r_radiosity value is set (in the console).
For about four hours I could not understand what was the matter, I changed the model, used various workarounds, but the handles were still too bright.
In general, if you have problems enter r_radiosity 4 into the console (for some reason, 3 by default). Note that this is considered a cheat (console cheat, you will not be VAC banned). The command simply won't work without sv_cheats 1.