Hey there Luis,

They are all the same base as the rest of the Vallejo Paints, doesn't matter if it is the metallic, regular or medium, or Model Color or Model Air.

Alex Vallejo (one of the owners of Vallejo Paint) has told me that the Model Air metallics have aluminum powder mixed in with them which makes them a little more brilliant.

As well the Model Air metallics, are thin enough to airbrush, but still thick enough to brush paint with.

You have quite a few colors.

Aluminum, Steel, Silver, Chrome, Gold, Brass, Copper, Metallic Rust, Stop Light Red, Arctic Blue Metallic, Gunmetal and Metallic Black.