Beta metroids are very rare metroids,
They only appear in Metroid II: Return of Samus,
a beta metroid is an Alpha Metroid with special genes,
and that they could even become a Queen Metroid.
A beta metroid appears as a boss in Metroid II: Return of Samus,
It is revealed after an Alpha Metroid that Samus meets,
the metroid alpha transforms into a larger creature.
These are similar to the Alpha Metroid,
but with bigger and longer legs,
They are also faster than alphas,
their usual way of attacking is crashing,
beta metroids have been replaced by Gamma Metroids,
after delivery for gameboy and gameboy color.