Cooper Bai has already represented Papua New Guinea twice, making his international debut in 2025 after a promising start to his NRL career.
The 20-year-old forward also played for the PNG Prime Minister's XIII against Australia that year.
Melbourne has signed Bai to a three-year deal, with the Gold Coast Titan due to join the Storm in 2028 and remain with the Titans for the coming season.
He has made 24 NRL appearances since debuting for Gold Coast in 2025, including 23 games and two tries during 2026.
Bai came through as a Burleigh junior and is the son of former Storm premiership-winner Marcus Bai.
Storm head of football Frank Ponissi said: "Cooper is an exciting young forward and a quality young man. He's made an impressive start to his career with the Gold Coast, and we're looking forward to supporting his continued development here in Melbourne,"
Ponissi said Bai would develop in the 12 months before his arrival, which coincides with Melbourne's 30th anniversary in 2028. Marcus featured in the club's inaugural 1998 season.