Well it hung around for a long time in the singular state (metallic hydrogen and solid diamond in a regular crystal). That was the low entropy state log2(1/num_states) = 0. That was also the metastable state. It was sitting on the metaphorical knife edge ready to fall off at any point. It did and now its in the new higher entropy and more stable state of "Splattered all over the lab and floating as a gas". log2(1/billions_of_states) = a much bigger number.
However it seems it was pushed by a laser light. In metastability in circuits we normally deal with thermal noise doing the pushing, but the noise is part of the system. So deciding what is in the system and what is not determines whether or not it's metastable.