aluminum foil is ductile. Foil can be rolled to only 0.007 mm thickness, but will still be completely impermeable and lets neither light, aroma nor taste substances in or out. The metal itself forms a protective oxide coating and is highly corrosion resistant. Different types of surface treatment can further improve these properties

Roast a chicken. Place the raw chicken on a baking pan, and tent it with aluminum foil. This will retain the juices in the turkey while baking, so as to cook completely through without burning. Remove the tent for the last hour of roasting, so that the chicken skin gets browned and crisp.

the only reason I can think of for using foil is to cover the roasting pan so you have less washing up to do. The problem with this is it prevents the formation of fond (those brown bits you find stuck to your pan after the chicken is done). fond is the base of a good pan gravy, and without it, you won;t get a good, rich sauce for your roast chicken. You don’t wrap a chicken when you roast it, because you will never get a nice crisp skin that way.