Metallic Swarmlets are a very terrifying creature indeed. Found in the depths of dark nebulae they feed on the iron and metal from asteroid rocks and in rare cases... Spaceships.
They are a very nasty pest to have to deal with thanks to their various nasty traits.
These small creatures are only 6 inches in length and are a silicon-based life form for sure. They gain nutrition from metal and can live of a small bit of metal for hundreds of years before starving to death. Their main body has very charp legs that are used to clamp into metal very tightly secretting a glue-like mucus that sticks them onto the metal and allows them to start to "drill" the metal with their mouth attached to their underbelly by dissolving it with nitric-level acid then sucking mucus into their bodies.
They communicate in a large group using a easily detected pheromone that they use to "smell" metal that they are seeking out than have a whole swarm of them latch onto whatever metal can be found. They often will stick onto a metal deposite for years rapidly slowling down their metabolism while doing so until they feel the need to latch off when they can't get anymore metal where they weaken their glues with their acids and pop off the metal to space to find more metal. Metallic swarmers can live for thousands of years, but thankfully reproduce at a very slow rate.
Metallic swarmers as their name suggest often stick around in large groups seeking out metal for nutrition and when they find metal will as a group start to latch onto as much of the metal coating it in a thick sheet of swarmlets. They see spaceships and asteroids alike as sources as food and will swarm a spaceship rapidly degrading its hull and screwing up various electronics and systems in the ship if they are left unattended to.
They are completly instinctual in nature and show no real intelligence beyond simplistic eat, move and reprodiuce functions.