In a blow to expansion sides and rival suitors Perth and PNG, 27-year-old Metcalf on Thursday inked a three-year deal to join the Dragons from next season.
He follows Scott Drinkwater, Phil Sami and Keaon Koloamatangi in committing to the Dragons, who have still not secured a full-time coach for the post-Shane Flanagan era.
Metcalf's signing could end up as the most significant of the lot, given the Dragons have struggled for direction from their halves since Ben Hunt left after the 2024 season.
Former Cronulla playmaker Dan Atkinson has not yet lived up to his billing as the club's star recruit for 2026, with the jury still out on young prospects Kade Reed and Lyhkan King-Togia as regular first-graders.
Kyle Flanagan, son of ex-coach Shane, is out of contract after next year.
Metcalf's arrival signals brighter days ahead for the last-placed Dragons, who enter Magic Round on a 13-game losing streak.
"I'm really excited to be joining the Dragons and grateful for the opportunity," Metcalf said in a statement.
"I intend to give my all to the Warriors for the remainder of this season before taking the next step in my career.Â
"It will be an honour to pull on the Red V and do everything I can to help the club move forward."
Metcalf was a leading contender for the 2025 Dally M Medal prior to suffering an anterior cruciate ligament injury last June, but has struggled for consistent NRL opportunities since recovering this year.
The second-placed Warriors have lost both games Metcalf has played this season, but have won all six when Tanah Boyd and Chanel Harris-Tavita started in the halves.
Metcalf only re-signed in October but this week received permission to negotiate with rival clubs, hopeful of becoming a regular NRL starting half again.
He did not travel to Magic Round with the Warriors for Sunday's clash against Brisbane, with the Kiwi club committing to give him space to decide on his future.
Earlier on Thursday, Warriors coach Andrew Webster insisted Metcalf's decision to explore his options was purely football related.
"This is not an argument or a blow-up or anything like that," Webster said.
"Luke wants to play NRL. He wants to be the guy who runs the team and steers them around.
"He obviously doesn't feel like he can get that here. And you know, we've lost two games, you know what I mean? The form (in his absence) has been unbelievable from everyone."
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