A method for forming a carbon nanotube array on a metal substrate includes the following steps: providing a metal substrate (11); depositing a silicon layer (21) on a surface of the metal substrate; depositing a catalyst layer (31) on the silicon layer; annealing the treated substrate; heating the treated substrate up to a predetermined temperature in flowing protective gas; introducing a carbon source gas for 5-30 minutes; and thus forming a carbon nanotube array (51) extending from the treated substrate. Generally, any metallic material can be used as the metal substrate. Various carbon nanotube arrays formed using various metal substrates can be incorporated into a wide variety of high power electronic device applications such as field emission devices (FEDs), electron guns, and so on. Carbon nanotubes formed using any of a variety of metal substrates are well aligned, and uniformly extend in a direction substantially perpendicular to the metal substrate.