I usually don’t include bolts and nuts in my CAD assemblies, but this was mostly do to not having CAD files for these things readily available.
I decided to fix that and create nut and bolt sets:
Metric Button Head: https://www.thingiverse.com/thing:3402872
Metric Socket Head: https://www.thingiverse.com/thing:3402887
Metric Nuts: https://www.thingiverse.com/thing:3402714
Each set contains *.STL, *.F3D and *.STP files and have been optimized for CAD.