A lamp has a metal layer to prevent light escaping in an undesired direction. A sealed envelope wall encloses an interior space in which an electrical element is arranged. The wall is partly coated by the metal layer, preferably at a lamp end opposite a lamp cap. A light diffusing or absorbing layer over a side of the metal layer facing the interior space prevents light reflection back into the interior space. For use as a vehicle headlamp, the metal layer may be silvery as viewed from the outside so that it is not noticeable.