When was metallic paint first used on a car?

There's no single definitive answer to when metallic paint was *first* used on a car. The introduction was gradual, with early examples being experimental or limited-production. However, the late 1920s and early 1930s are generally considered the period when metallic paints started appearing, though they weren't widely adopted until much later. These early uses often involved the addition of aluminum flakes to existing paint formulations. The widespread commercialization and popularity only really took off post-World War II.