While not being the most popular type of siding, which you would have realized visiting a store such as Home Depot. It is, however still used in a lot of construction, for example in house framing and is used for various purposes by construction contractors. However, it is used as weathered steel siding, also known as Corten.
Steel has an approximate density of 8 g/cm3. With there being 1000 mm3 to one cm3, the density is 0.008g/mm3 for aluminum, which equates to 0.000008kg/mm3.