Samus comes from. There is a cameo of Kirby's Dream Land 3. Samus also appears in this same level. These creatures won't do any damage but instead stun Gooey or Kirby by holding onto their heads. You need to destory them with Ice. You will get a Heart Star from Samus if you destory the metroids.
In Metroid Edit
These are parasites that rome Zebes. They have to be defeated by Samus for the sake of the galaxy. Samus once had a bond with one who sacrificed itself for her in the end. They can only be defeated with freeze guns.