I painted something a while back.  I made it a dramatic dark  dark blue.  I wanted metal flake in it so I bought some and put it in and was disappointed at the result.

I think I needed to put the flake in a clear coat top layer.

I'll prolly try to fix it by applying a slight scuff and  a clear flaked top coat

Probably not the same thing but we painted the bathroom with paint from Sherwin Williams glitter paint. The glitter was mixed in but when it was rolled out the glitter seemed to float to the surface and wasn’t covered by the paint

As a test for a finish with glitter I applied a coat of poly, let it dry.  Then went with second coat and sprinkled glitter into it as it skinned over.  No sanding afterward.  Then 2 more coats of poly and just lightly sanded with 400 grit and one last coat.  Looked okay.  Did not take pictures but that piece was around for a couple of years and seemed to do okay getting tossed about on the various horizontal junk repositories, I mean workbenches. 

I would add some blue coloring (dye not paint ) to the clear. This will give the metal flake a blue tint and not silver if this is what you are looking for.   As always try on a sample, not the project.  Roly