99.5.5.5.5.5.5.5.5 chance they will. Metynnis species are primarily vegetarians so they will eat live plants with joy.
The only plant I have been able to successfully keep with my Metynnis lippincottianus is Anubais. They destroyed every single other plant. I was worried about the geos, severum, chocolate, and royal pleco.
Surprisingly, I have never noticed any of my Myleus (red hooks and black bars) go after plants, it is my firm belief that Myleus are more carnivorous than metynnis and like meaty foods too.