Metals such as aluminum can be formed into thin sheets because they are

Metals such as aluminum can be formed into thin sheets because they are Malleable

Explanation:

A malleability is the property of a material that describes its ability to be deformed under pressure or compressive stress such that it can be moved about spread out without breaking (analogy dough in bread making). As such a malleable metal can be made into flat thin sheets by applying compressive stress such as hammering.

In the process, malleable metals such as gold can be flattened into a metal leaf, such as gold leaf

Malleability is primarily present in metals as nonmetals are likely to be brken when subjected to compressive stresses

Aluminium, gold and silver are highly malleable, while zinc is malleable between the temperatures of 100 °C and 200 °C.