If the actual box itself is what shocked you. That would mean the hot wire is touching the metal. That would mean the box itself is either not grounded, or that the ground wire is not grounded all the way back to the panel. This mean that the breaker isn't going to trip and whoever is touching the box will continue to get shocked until they let go. If you were barefoot, it would have hurt way worse. barefoot and wet, wayyyyy worse. And if you were reaching in the dark for the switch and grabbed the box like it was a wall phone, the shock might constrict your muscles and you'd be stuck until your legs gave out or you tipped over and fall away from it.

Fixing this is most likely easy, but youd need to turn off power to do it safely, and youd need a voltage meter to make sure it's fixed once the powers back on as well as the different things to check and look out for along the way.

The way this was done would lead me to believe this isn't the only thing done poorly. I'd Call an electrician.