alum, metal or what ever material is up to you as far as u willing to pay for it
but in the market usually its made of aluminium
this 1 the above estimated size 4m x 4m
aluminium powder coated
and it will cost around RM 2-3k or even more depend on thickness & specification & quantity ordered

beside for sunshade, curtain, looks
it can also use to cover up your aircon compressor unit
based on the photo there, that area might be a aircon ledge / vent