Metal Energy (Basic)
It was first released in Diamond & Pearl, as Metal-type Pokémon were getting to be much more prevalent in the TCG by this point, much like their counterparts in the games. Unfortunately, both the old Metal Energy as well as the old Darkness Energy, which were originally released in Neo Genesis, were classified as Special Energy cards. Being such, only four copies of them were allowed in a legal deck, and combined with their rarity, many players had to go to great lengths to have a deck that even attempted to mix in a few Metal-types. With the new, Basic Energy version of Metal Energy, however, an unlimited amount are now allowed in a deck, though there is no specific advantage to using them, unlike their counterparts.