Exterior wall covering is most commonly aluminum riveted to vertical posts that run from the floor to the roof. The thickness of the aluminum side sheets is expressed as a decimal fraction of an inch and can vary from .050 to .090 (e.g., .090 is 9/100 of an inch thick.)
If pre-painted aluminum sheets are used, there is no need for painting later, except for any additional exterior designs you wish to add. Side sheets can be attached to vertical posts in two ways, exposed rivets or smooth side, where rivets are concealed.
One thing about smooth sides is that it's best to paint it after assembly vs. using pre-painted sheets. That's because smooth side design requires the vertical edges to be bent 90 degrees using a large press. This process usually cracks the paint on pre-painted sheets. Therefore, smooth side design is built with unpainted sheets, which must be painted later. The cost to assemble is similar either way except that smooth still needs to be painted after assembly, which is an extra cost. However smooth sides offer a smoother surface for applying paint and graphics.