Well, aluminum oxide is an ionic compound as it contains elements categorized as being metal and nonmetal, aluminum is metal and oxygen is nonmetal.
Methane is a covalent compound as it contains elements that are categorized as nonmetals. Hydrogen and carbon.
Also if you took the electronegative values of each element in methane and subtracted the larger one from the smaller one, it would result in a value that is found within a particular range of electronegativity differences that represents it's a covalent, more specifically it can help distinguish between polar covalent and or Nonpolar covalent compounds.
