Actually, that still wouldn't work. That device is definitely a famiclone and takes cartridges. Metroid was released on Famicom Disk, not cartridge.
So unless it's one of the games included on the 76 games (and they usually don't include it or other larger game ROMs) that comes with it, he still won't get Metroid. A 72 pin converter is horrible on these things. I have a Game Axe Color, which is basically a very old version of this and it came with a converter. It makes the cartridge flop around and freeze the game, so the portability goes away too.