This is a suit of armor from 16th century Spain. How common were steel shields in the medieval/early modern era?
>>3303303
Well some steel shields were used in very specific situations in the WWI, (pic related)
>>3303387
Like stationary trench defense?
>>3303303
They weren't really shields but, instead, bucklers. The steel made the buckler heavy and so a small size was required. The shield had largely fallen out of use following the advent of plate armor but still found its individual uses; for example in the form of the Spanish tercio blocks where the front ranks of the formation fought with swords and steel bucklers. So as to your question the shield would have been somewhat uncommon but certainly not unknown.
>>3303395
yes, and as cover for shooting
>>3303845
>Were those thick enough to work?
Worked well against handguns and grenade shrapnel, but poorly against rifle and machine guns if they were too close, also this shields were heavy so were be more a inconvenience than an advantage.
>>3303303
Were they really effective?
>>3303303
As far as I'm aware steel/ironshield were pretty much non-existant besides certain smaller shields like in OP's image. If I were to speculate I would presume that it had to do with wood, potentially wrapped in leather etc makes for a perfectly adequate defense, while also being far cheaper to make and replace.