Solomona, 20, grew up in Auckland but is a product of the Storm’s youth system, and can play full-back, wing and centre.
Broncos coach Tony Rea said: “Denny is a talented individual who has been really brave in his decision to come here. He’s been sitting behind Billy Slater as his understudy at Melbourne but has taken a decision to come here. This is a way of putting himself out on his own stage.
“He had a contract at Melbourne, which he left to join us, and had the full support of Melbourne and the Broncos to do that.”