The metalflake and candy has been a heavy part of the kustom kulture since the 60s, there were cars like that cruising Bellflower and Woodward since the early 60s, and it all later evolved into the lowrider scene late in that decade; as that happened, the 'flake became toooo related to lowriders so customizers let that style aside and concentrated on metallics.
Only lately, in this free-for-all era, has this style had a comeback. It is one of the hardest and more expensive ways of kustomizing a car because getting it really right not only involves the paint, but a load of details as well. for example, in the '60 that Keef posted, as awesome as it is, the engine is toooo chromed up, too nice and way too modern, it's not era-correct.