Repeater for getting Wi Fi signal into all-metal outbuilding?

My all-metal (no windows) studio outbuilding blocks my existing Wi Fi signal completely. It is 100 feet from my router.
I need a weatherproof repeater setup where where I can mount a receiver on the exterior of the metal building and get the repeater signal through the metal wall into the interior to broadcast the Wi Fi signal inside.
The weatherproof repeaters I have looked online have both the receiving and sending antennae on the outside of the building. I think that I need to get the signal into the metal building interior using a cable since the metal walls without windows act like a Farraday cage. I can visualize extending a cable through the wall and placing the repeater antenna inside the building, but I'm incompetent to do that myself plus it would void any warrantees and might damage the unit.
Any specific recommendations?
Art
BTW: The existing router Wi Fi signal is very robust and easily serves another building (with windows) which is further away than the metal studio.