Montgomery joined the Mets on a minor-league contract Tuesday, Robert Murray of FanSided.com reports.
The 32-year-old lefty owns a 3.84 ERA in 541 career MLB innings, but it's been several years since he pitched at that level. He struggled to a 4.95 ERA in 2019 and then threw just 5.1 innings in 2020. He spent last season with the KBO's Samsung Lions but didn't fare well there, either, posting a 5.26 ERA and getting suspended 20 games for throwing a rosin bag at an umpire.