Many bonds share characteristics of both ionic and covalent bonding. They are called polar covalent bonds and they tend to occur between atoms of moderately different electronegativities.
In polar covalent bonds the electrons belong predominantly to one type of atom while they are still partially shared by the other type, as illustrated in the pictures of the valence electron densities.
In addition to covalent, polar, ionic and metallic bonding there are intermolecular forces which contribute to the stability of things. These include dipole-dipole forces, hydrogen bonding and London dispersion forces.