Metrion

metreon is a type of energetic particle. 

Traveling through metreon gas collapses a starship's warp field, leaving warp drive functional, but unattainable until the starship leaves the cloud. Impulse drives are also dangerous to use in a metreon cloud.

In 2154, when entering a subspace corridor in the Delphic Expanse, Reed suggested that Enterprise enter above a pocket of metreon gas, to hide their signature from the Kovaalans. (ENT: "E²")

In 2371, a surge of metreon radiation destroyed the USS Olympia's engines, causing it to crash on a planet in the Ruthan sector. (DS9: "The Sound of Her Voice")

Metreon isotopes were also the primary constituent of the metreon cascade, a weapon used on the Talaxian moon, Rinax. (VOY: "Jetrel")

There are pockets of unstable metreon gas in the Briar Patch in Sector 441. Commander Riker used this to his advantage when fighting the Son'a in 2375, when he created the "Riker Maneuver". (Star Trek: Insurrection)

Later that year, in the Delta Quadrant, USS Voyager scanned a planetoid, and it began emitting a resonance wave. Just as Voyager raised shields, the planetoid exploded, and enveloped Voyager in a cloud of metreon gas, knocking their impulse engines offline. (VOY: "Think Tank")