They are harder and tougher. Magnesium is used to fabricate car parts like wheels. Calcium reacts with water. Magnesium clearly doesn't react with water or else it couldn't be used in car parts. The halogens, F, Cl, Br, I, At, are nonmetals.
Halogens have lower melting points than the alkali metals.
The noble gases, He, Ne, Ar, Kr, Xe, Ra, are nonmetals. The noble gases are very unreactive. They were once called the inert gases. The noble gases are so unreactive they are used to protect materials from reaction. Welding is done using argon atmosphere to prevent oxygen in the air from reacting with the hot welded metals.