sirdvae, the point of contention was that melting metal objects would count as producing bars the same way as smelting ores, i.e. they can be demanded. But to counter that, you said that you accidentally(?) forbade some bars still owned by merchants, and then seemed to claim that the fact that those bars were not demanded in moods was evidence that melted bars can't be demanded. I'm not saying you're wrong about melting, I'm saying that this paragraph does not in fact say anything about bars from melted items not being "demandable":
Ive posted what I have because that the experience I had. I definately had dwarves with a preference for a metal I had bars of that used the bars I wanted. To start with i was atom smashing all the goblinite but then I ended up with a few bars of metals I didnt want via forbiding all bars via the stock screen when a merchant was in the depot (so I forbidded the merchants bars and they "became mine"). after this the preferences still did not mandate the material (I was still forbidding the metals I didnt want to be used)
You just say you used to atomsmash goblinite, but apparently stopped. And then you got some bars by forbidding the merchants'. I repeat, neither has any bearing on whether bars from melting can be demanded. I can only judge your evidence based off what you say, not what you did in your fort. Or said in your most recent post, but not earlier. You may have been implying it earlier, but you didn't state clear evidence.
About the boasting thing: I do pick my words carefully, e.g. both "I wouldn't boast..." and "(sounded like one, initially)" were phrased that way for a reason. I wasn't actually accusing you of boasting, just saying that your first post in this thread did sound somewhat boastful ("I've got lots of artefacts, lots of them weapons/armor, practically all out of steel, too"), but I also said that once you mentioned that it was an artifact-generation testing fort, the context changed entirely.
Lastly, forbidding all but the desired metals is a (small) exploit in my books (which is not to say I haven't used it a few times, but normally not): I think that if it was intended for the player to be able to cherry-pick materials for moods, then there would actually be a UI for that, like for regular weaponcrafting, for example... Of course, even if the forbidding trick, or restricting materials via burrows, were fixed to remove them as possibilities for the savvy player, the savvy player would still find ways to get mooders to use the (non-demanded) materials they want used, not what the dwarf would pick: for example, locking/walling potential mooders in rooms with only the materials desired/dumping in any decoration materials.
tl;dr: Artifacts are meant to be random, and a product of a dwarf going temporarily crazy; what makes you think you're meant to be able to pick the materials in them?
Shield are always good artifacts! Light Materials are considered better though....
Not particularly. Shield-bashing can be quite useful. A black bronze shield is good for that.
As for this, the correct, or at least better, statement would be "Not necessarily". Light materials are good for less weight, heavy materials for shield-bashing, and there are some relatively marginal situations (at least in vanilla) where ideally you'd have them at least be fire-safe. Nether-cap is even dragonfire-safe, but since the shield is only affected by the tile the wearer is standing on, not by the direct dragonbreath, which is just blocked, it doesn't really matter much, unless a dwarf drops the shield on the battlefield, and it gets breathed on after that.