Standard aircraft fasteners all are American and they are in Imperial units. As far as I can tell, non-American companies like Airbus either use the American standards, or they create their own in-house standards and send them out to vendors.
I don't do buildings. Someone somewhere needs a reliable fastener. Someone writes a specification in units they like. Be glad no one uses cubits.
One option is to go to the IFI (Industrial Fasteners Institute)website. Go to the standards search page and look for IFI or ISO metric fasteners. The website provides a list of all the metric fastener standards based on type of nut, screw, bolt, washer.
What industry, what type of fasteners, what nations for supply and manufacturing? All of these will affect which group of metric standards that you would be interested in. There are a massive number of different specifications that you can choose from, but you want to select those that are appropriate for your situation. There is no magic answer that cuts across all industries.
I managed to get a Bossard catalog which describes all metric fasteners in terms of their governing ISO or DIN standards. It's a great reference, if you can get one that is.
