I'm now dealing with a warehouse with insulated steel exterior wall panels. I'll need to secure camera mounts at several outdoor positions on these walls. Also, I'll be installing an outdoor alarm bell/box. I see where exterior lights were installed some years ago and the methods used by the electrician to secure the lights are interesting. It's as if the electrician couldn't decided on which method was best, so a few different methods were used. The previous security integrator mounted an exterior camera and left a few holes around the camera, unsealed, which appear to be failed attempts. I haven't taken down the old camera yet, so I don't know how it was finally secured. All devices will be mounted between 10 - 15 feet high.
These walls appear to be more challenging than wood, stucco, or concrete.
Insulated steel wall panels have thin 24 - 26 gauge sheet metal separated by 3" void filled with fiberglass insulation. These particular panels have a staggered pattern, high/low outside panel. The panels are secured to the steel frame of the building with heavy duty rivets. You can push on the panels and watch them flex inward, that's how thin they are.
Using self tapping sheet metal screws will provide little to none holding strength on such a thin gauge sheet metal and are easily stripped by over tightening. In high winds these would obviously loosen and fail.
Drilling through and securing with a bolt/washer/nut combo would provide good holding strength, but will compress and distort the exterior panel, and it may be difficult to seal against water infiltration. (The electrician did a few of these, they are not consistent with the method, and it looks like there must be a better way than the way they did it.)
Using nut inserts, "nut serts", rivet nuts, seems to be the best way to secure these devices without compressing and distorting the panels. But the holding strength is dependent on just one thin exterior metal sheet. I'm leaning toward this method.
This is an example of the kinds of things that would be nice to discuss in a future class.