Metals are mostly of medium to high density —
only magnesium, aluminium and beryllium can
compete with plastics in this respect. Many have
good thermal stability and may be made
corrosion resistant by alloying.
They have useful mechanical properties and high
toughness, and they are moderately easy to
shape and join.
It is largely a consequence of their ductility and
resistance to cracking that metals, as a class,
became (and remain) the preferred engineering
materials.