Boiled linseed oil can be use for both wood and metal, it is a popular items for wood treatment primarily for interior use. It leaves a lovely and smooth finish on a wooden surface. Boiled linseed oil soaks deep into the wooden fibres, thus giving its shiny look but not glossy.
Boiled linseed oil also helps to preserve metal, by protecting the surface from oxidation. Thin coating work best and generally applied to non-moving parts / workshop tools.