Welch has signed on until the end of the 2022 season, with the State of Origin star quickly rising as one of Melbourne’s best players in 2020.
Storm general manager of football Frank Ponissi commended the 26-year-old’s last 12 months in the NRL.
“Christian is having an outstanding 2020 to back up earning his first jersey for the Maroons last year,” Ponissi said.
“What we like a lot about Christian is the leadership skills that he possesses on and off the field and the dedication he puts into improving his game.
King will enter his sixth season of NRL next year after joining the league with Gold Coast, singing until the end of 2021.
The 23-year-old joined Melbourne halfway through 2019 from the Titans and has since featured in Craig Bellamy’s side on 12 occasions.
“There is definitely many more NRL matches in Max’s future,” Ponissi said.
“I’m sure he’s looking forward to getting in a full pre-season and making the most of 2021.”
Howarth will join the Storm senior squad for the first time after singing a deal until the end of the 2022 season.
The Melbourne newcomer has featured for the Australian Schoolboys and Queensland under-18’s and will complete year 12 in Brisbane before relocating to Melbourne.