Gilyard was also known for his supporting roles in the 1980s action films Top Gun, as Radar Intercept Officer "Sundown", and Die Hard, as terrorist computer expert Theo.

[1] His family was originally from New Orleans, Louisiana, but Gilyard grew up on Air Force bases in Hawaii, Texas, and Florida.

[1][3][4] During his young adulthood, Gilyard lived in the San Bernardino suburb of Rialto, California, and attended Eisenhower High School.

He was an excellent student, graduating in 1974, and afterward spent a year as an Air Force Academy cadet before leaving the service to attend Sterling College.

[1] In 2003, Gilyard returned to school, receiving a Master of Fine Arts in theatre performance at Southern Methodist University.

In 1982–1983, Gilyard was cast in the final season of the NBC TV series CHiPs as Officer Benjamin Webster, opposite Erik Estrada.

[citation needed] Gilyard's movie debut in 1986 was as an F-14 Tomcat radar intercept officer, LT. (JG) Marcus "Sundown" Williams, in Top Gun.

Andy Griffith suggested to Gilyard that he move there, too, which he did, before departing to work on a pilot for another series at CBS the following year.

On January 17, 2016, Gilyard performed the role of Hoak Colburn onstage at the University of New Mexico's Popejoy Hall in the Neil Simon Festival's Driving Miss Daisy, opposite his former Walker, Texas Ranger co-star, Sheree J.

Two years later, Gilyard reprised his role as criminal gang member Theo from Die Hard, alongside star Bruce Willis, in a commercial for Advance Auto Parts' DieHard brand of car batteries.