If you can supply enough heat and enough electricity, any metal can be formed via electrolysis. However, a lot of times it's easier and cheaper to do it chemically (I.E. with carbon). In order to know which ones can be extracted from the ores via carbon, you just need to find the list of standard reduction potentials. Anything that is higher up on that list will replace something which is lower down on that list. So if a specific metal is below elemental carbon on the list, than carbon will be able to replace it from the molten salt. The metals which are generally formed via electrolysis are those which are high up on that list such as sodium, potassium, aluminum, etc.