As far as the heating pad, if this is a typical human use heating pad that's functioning properly, they never get too hot to safely touch, so they won't heat up metal that much either.
You can see my heating pad set up here, note that the entire frame is wire: https://www.backyardchickens.com/articles/short-on-time-recycle-a-prefab-brooder.73985/
I start on high and dial it down from there. It's always recommended to test it in advance so you get an idea how hot it runs (I use my hand, if using a thermometer remember you are not checking ambient air temperature but rather the surface temp of the pad), and also run it for about 24 hours before the arrival of chicks.
You can see my heating pad set up here, note that the entire frame is wire: https://www.backyardchickens.com/articles/short-on-time-recycle-a-prefab-brooder.73985/
I start on high and dial it down from there. It's always recommended to test it in advance so you get an idea how hot it runs (I use my hand, if using a thermometer remember you are not checking ambient air temperature but rather the surface temp of the pad), and also run it for about 24 hours before the arrival of chicks.
Yup. But note that's the "minimum" - more space is always better. 4 chickens in 160 sq ft will be far happier than 16 in the same space.According to the general guidelines/minimums, 10x16 is enough for 16 chickens.