What types of elements tend to combine to form molecular compounds?

Most molecular compounds are composed of the atoms of two or more nonmetals, ionic compounds on the other hand, are formed from a metal and a non metal. All of them, with the exception of the "Noble" gases (group 8 in the periodic table). Even these have been forced to form compounds under unique laboratory conditions, with the exception of Helium. No stable compound of Helium is known