Homebrew developer LOO-E is porting the original NES Metroid to the Game Boy, it has been revealed.
M2NES: Zebes Revisited is actually a ROM hack which is built on the framework of Metroid II: Return of Samus, a Game Boy exclusive sequel released in 1991, which was later remastered for the 3DS as Metroid: Samus Returns.
It remains to be seen if this hack flies under the radar of Nintendo; it famously took the excellent AM2R (Another Metroid 2 Remake) down via a DMCA in 2016. The fact that it's a ROM hack should be enough to avoid any legal action.
The original NES Metroid was famously ported to the Game Boy Advance as Metroid: Zero Mission. The most recent entry in the franchise is Metroid Dread on the Switch. Metroid Prime 4 is currently in development.