How do you mount stuff to sheet metal walls - especially when you don't have access to the other face?
It depends on what I am mounting.
If it was lightweight I might use a #12 sheet metal screw.
Than I may move to toggle bolts.
Move up again with unistrut and toggles or uni-strut tec-screwed into the building structure under the tin.
Assuming the FMC contains type "W" conductors it would be allowed.
Strangely IMO the liquid tight flexible metal conduit is in violation of 225.22