If a molecule has polar bonds, does it also have Dipole-Dipole IMF’s? Explain.

Question

(This is my explanation) This depends on whether the molecule is polar or nonpolar because the polarity of a molecule is not only determined by the presence of polar bonds, but also by the shape of the molecule. Dipole-dipole forces occur when the positive part of a polar molecule is attracted to the negative partial charge of another polar molecule. In a nonpolar molecule, there may still be polar bonds, but the dipoles cancel each other out. Hence, dipole-dipole forces only occur in polar molecules.
*******Would you mind checking it?

Answer 1

I think the first part of your explanation is OK. I think, perhaps, your second part needs a little work if I understood it correctly. From the way I read the second part here are two examples I thought of.
H2, N2, O2 are non-polar molecules and the bonds are non-polar so I'm having trouble understanding what dipoles cancel out. There aren't any dipoles.
Another example is CH4. The 4 C-H bonds are polar (slightly) but the shape is tetrahedral which makes it symmetrical; thus the molecule is non-polar. Again, what dipoles cancel out. There aren't any dipoles or have I missed something?