Frank Ocean has been called a mirror to the millennial generation. The 31-year-old singer-songwriter flouts music-industry conventions and gets away with it. He spurns social media, releases songs sparingly and didn’t submit his hit album “Blonde” for Grammy Award consideration.

One of the first artists to blend R&B, soul, rap, rock and electronic music, he has gained a following for writing about how the privileged struggle to find purpose. Here are five reasons why music critics and industry executives consider Mr. Ocean...