The change will take place at the end of the First-Year Player Draft signing period on July 17.
MLB.com has confirmed that Metzler will move up from his role as assistant director, amateur scouting. Meanwhile, Harrison will take on the position of senior advisor, scouting/baseball operations.
"These changes reflect both our confidence in the direction of our amateur scouting department and our hope for its continued evolution," said Matt Silverman, Rays president of baseball operations. "I am grateful for R.J.'s leadership of the department through this year's Draft and for the past 10 seasons. It's only because of his guidance and mentorship that we are in position to take these next steps."
Harrison was one of the first hires by the Rays' organization when he joined the club in September of 1995. He was named director of scouting after serving as assistant director of scouting for one year.
Harrison had served the club as a western United States crosschecker, national crosschecker and national scouting coordinator.
"Very few people get to have as long a run in the director role as I have had, and I am very thankful to the organization for their faith in me over the years," Harrison said. "I look forward to many more years helping grow our baseball organization and plan to enjoy those changes ahead."
The team also named James Click director, baseball operations; Matt Arnold, director, player personnel; and Bobby Heck, special assitant, baseball operations.
Some of the top players drafted during Harrison's tenure as the team's scouting director include Evan Longoria, David Price, Alex Cobb, Desmond Jennings, Matt Moore, and Kevin Kiermaier.