Here's why:

* Electronegativity: Oxygen is much more electronegative than carbon and hydrogen. This means it attracts electrons more strongly, creating a partial negative charge on the oxygen atom and a partial positive charge on the hydrogen atom in the hydroxyl group.

* Polarity: The difference in electronegativity between oxygen and hydrogen creates a significant dipole moment in the hydroxyl group, making it a polar functional group.

* Methyl Group: The methyl group, with its carbon and hydrogen atoms, has very similar electronegativity values. This results in a much smaller, almost negligible dipole moment, making it nonpolar.

In summary: The hydroxyl group is highly polar due to the electronegative oxygen atom, while the methyl group is nonpolar because of its similar electronegativity values.