Question

Which element can combine with metals but also readily combines with non-metals very similarly to the way the alkali metals combine?

Answer 1

That would be HYDROGEN.

Because hydrogen has a single electron for the most part, an electron that will readily be lost to form the hydrogen ion it is able to bond with both non-metals who it can give an electron to form covalent bonds (eg. HF, HCl, H₂O, HBr) while also giving up its electron to an alkali metal to form Ionic bonds (eg. KH, Na H)