This is The Army Painter Warpaints Fanatic Metallic: Gun Metal - 18ml Acrylic Paint

Warpaints Fanatic Metallics are a stalwart for hobbyists of all kinds. The Metallic paint is non-toxic and water-based and thanks to their unique formulation provides amazing coverage and a dazzling shine.
The Metallics utilise a specialised blend of aluminium flake and mica for the best combination of coverage and sheen, making it more shimmery than traditional metallic paints as well as providing better coverage. This is especially noticeable when painting with paints where you traditionally would apply multiple layers to achieve great coverage, like gold.
In the Warpaints Fanatic range, you’ll find 18 metallics, so there is sure to be a colour that meets the needs of your next project. And if not, the Metallics paints mix effortlessly with each other, so you can create any combination of colours that you dream of.