Despite the perk description only mentioning weapons and armor, it also allows additional materials to be salvaged from scrapped settlement objects. For instance, a baseball player statue that requires 10 copper to build normally yields nothing when scrapped, but having rank 1 of this perk allows the player to salvage 2 copper from it, and having rank 3 increases the yield to 5 copper.
Modified weapons will produce additional components
Certain mods and prefixes indicate whether some components may be scrapped from them, while other components are linked to the base weapon. For instance, weapons with the "muzzled" or "silenced" prefix will nearly always yield aluminum (though the quantity depends on the base weapon), while wood and copper are tied to the base weapon (double barrel and combat shotguns and hunting rifles in the case of wood, and pipe weapons for copper), with the modifications determining the quantity. Unlike other resources, wood is often present with less technical mods, with the "short" versions often providing the most.
The same applies to armor, but the effect is less dramatic (significantly less-common modifications are needed to extract the more uncommon/rare components).
The highlighting effect from rank 2 applies to junk and containers containing junk with components that have been marked for search only, not to weapons and armor.