I have all sorts of old magic cards, for example m12, X ,vintage, m13, I'm just curious if I can add any of these cards to my Commander deck that I have now ,or would it be illegal??
Yes, you can use any cards you could in Vintage (except for the banned list).
It'd be pretty silly to have to build 100-card decks with limited colors without being able to use a nice large card pool! And if you look at commander deck lists people have published online, it should be pretty clear that a lot of the really popular cards are old ones. (Not that M12 and M13 are really that old...)