[quote=Queen Raidne]
Your first link to metroid actually goes to the IC page for some reason.I'd just add a couple of things about the immune to weaponry part (garnered from the wiki):"Sensitivity to certain sonic frequencies" - http://metroid.wikia.com/wiki/Metroid_(species)#Physiology_and_morphology, toward the bottom of the section.And I imagine that X-Ray lasers can damage them, more-or-less, based off of Samus' use of the Nova beam to kill phazon metroids by aiming at their... nuclei(?). According to the wiki, it's a "high-frequency electromagnetic radiation beam" weapon, which means X-Rays or Gamma rays. Not that, I think, anybody's going to get X-Ray lasers any time soon.Anyway, you're accepted! Throw up an intro post when you're ready.
[/quote]

That was actually only implemented in Metroid Prime 3, and you never encounter standard metroids in the Prime Trilogy. In all actuality, there's no telling how high-frequency energy weaponry would affect standard metroids. The lore of the series states that that the non-standard metroids encountered in the Prime Trilogy are mutated variants, either through differing evolutionary paths due to differing environments, mutation through Phazon, or via direct genetic manipulation by other species (namely, Zebesians). Most of these mutated variants do still have weakness to cold, but lack the total vulnerability to all other forms of attack. Such mutations can actually absorb too much energy and explode, where standard metroids have an infinite capacity for energy absorption.

I realize it's ironic that the "natural" metroids are superior to the genetically engineered variants, but that's just how the lore is. There is only one instance where a genetically engineered variant is superior to the standard variety, which was engineered by the Galactic Federation, which are the humans. They created the [url=http://metroid.wikia.com/wiki/Unfreezable_Metroid]Unfreezable Metroid[/url], which is a variant with its weakness to cold eliminated without any of the side effects of previous variants that are also immune to cold. These metroids are totally indestructible, which is why I'm not putting them here.

I'll include the sensitivity just so they won't be totally unstoppable, since most of the people here wouldn't have cold-based weaponry that I know of. However, this is nothing more than a sensitivity, rather than an outright weakness like the vulnerability to cold. I should also note that they can't circumvent the vulnerability to cold, but later stages of evolution could possibly overcome the sensitivity to high-frequency energy attacks if it proves necessary.

EDIT: It isn't really obvious, but the metroids do have a problem. They are very few in number and the hex didn't have a Queen Metroid, so they're stuck with low numbers until an Omega proves to be special and evolves into a Queen. The highest stage they have at the moment is Omega, and there's only one of them. This Omega is also not one of the special kind, so it's hit the end of its evolutionary path (that of being the ultimate predator and having no real need to evolve again unless genetically tagged as a Queen).