He played as a catcher in Major League Baseball from 1970 to 1984 for the Pittsburgh Pirates, Houston Astros, Detroit Tigers, Chicago White Sox, and San Francisco Giants.

[1][2] Milt May was selected as an infielder in the 11th round (237th overall) of the 1968 Major League Baseball draft by the Pittsburgh Pirates out of St. Petersburg High School, Florida who then converted him into a catcher.

[3] He was a good handler of pitchers and a left-handed line drive hitter who rarely swung at a bad pitch, but also was reputedly the slowest runner in the majors for much of his career.

[1] In the seventh inning of Game Four of that series, his pinch-hit single drove in Bob Robertson with the winning run in a 4–3 Pirates victory.

[5] Tragedy struck the Pirates in late 1972, when outfielder Roberto Clemente died in a plane crash.

[6] However the experiment ended by July when it was determined that Sanguillén could not adjust to playing in the outfield and May was back on the Pirates' bench.

After only one year in Chicago, he signed a five-year, $1 million free agent contract with the San Francisco Giants on December 12, 1979.

[2] He spent the first half of the 1999 season with the Tampa Bay Devil Rays and was later named a pitching coach for the Colorado Rockies.