A more electronegative atom will pull the electron pair away from the other atom. The more unequal the sharing, the more polar the bond. Flourine is the most electronegative element, oxygen and nitrogen are also very electronegative. The O-H bond in water is polar because oxygen is more electronegative than hydrogen. The C-H bond in methane is not polar, because there is a very tiny difference in electronegativity between C and H. Hydrogen bonding Molecules that have hydrogen bonded to F, O, or N can form special intermolecular bonds called Hydrogen bonds.
Water is a very important example of hydrogen bonding.