The advantage of having metal sign is that it is lighter,good to dismiss heat from the working LED,it has almost no size limit as long as vehicles can take.It can be huge and strong outdoors being weather resistant,OK to take a variety of mounting ways. Metal sign can be made in aluminum, stainless steel,copper,or brass,with various surfacetreatment or painting colours. You can have the light from the front,back,or side,LED can be in various colours.