I would never, never live in a metal house.
Most containers have been heavily sprayed with pesticides many times during their lifespan so that should be taken into consideration.
If I needed a dwelling, I would look into this method of construction:
http://www.daycreek.com/dc/html/dc_cordwood_masonry.htm
http://en.wikipedia.org/wiki/Cordwood_construction
In fact we’re thinking of building a small pump house that way just to see if it works. Any and all sizes of wood can be used.