[@Cube]
So hold on, where does the magic even come from? Why does mana need to "reach" my body? Does it come from the outside world and despite a mage being able to attract it like a magnet it can pass through the entire world but be stopped by a thin sheet of metal? 
If I or anyone else would play a mage I would expect us to know how magic works OOC and In-Universe in quite sophisticated depths. Of course "it's not researched by the masses" is a good reason for common people to have no idea, like it always is in fantasy, but I take it mages who study magic all their lives as it is required here would know exactly how and why shit happens, else magic would not be possible to use.