Back in the stone age of model railroading, before styrene became available, modellers wishing to depict metal either used wood that had had several coats of sealer applied (sanding between coats, of course), or cardstock, such as Strathmore board. You could also buy "shapes", such as I beams, H columns, and angles and channels, all made from basswood. (You can buy balsa wood, in sheets or strips, but its coarse grain soaks up paint like a sponge and it's quite soft) You can still use these materials, but my preference would be styrene. You can buy it in sheets, either plain or milled to look like various kinds of siding, both wood and metal, and there is a wide range of structural shapes available. You don't need to use a sealer, as there's no grain to hide, and construction is fast and easy using a solvent type cement. Large structures in either wood or styrene both need to be properly braced to prevent warping, so they're about the same in this respect, although the styrene is still faster. If I was making a "wooden" structure, I'd use styrene for that, too, as you can make styrene look like wood better than I've seen anybody make basswood look like full-size wood. With the better glues available today, wood models may stand-up better than they used to, as joints often failed after 25 or 30 years of sitting around. Many modellers still like to work with wood, so the choice is yours. I've worked with both, and styrene is my preference, by far.
Wayne