Force Metals, when refined, typically take the shape of a small hexagon that reploids insert into their armor.

In 2170 a large meteor fell into the Pacific ocean. A team of researchers went looking to figure out what it was and if it held any useful properties. What they discovered though was beyond their dreams…

After recovering a sample of the meteor's ore, they conducted many tests on the small sample they had. During those tests they realise how valuable a discovery they had made. They presented their initial findings and after several gruelling trials and appearances before government they were given full funding to create a massive floating platform-like city to investigate, mine the meteor and research the resulting ore.

Thus the construction of Giga City began in early 2172. Though due to a successful Maverick attack in 2175, Giga City's construction was significantly delayed. It took several extra years to complete the project (with Giga City being fully completed in 2192) and begin the mining process.

Progress was slow at first, but soon enough they began to get more results. Results they were largely kept secret until years later.

Force Metals (the refined form of the meteor's ore) provide the user with a powerful boost to their abilities. Each Force Metal contains a massive amount of energy that a reploid can tap into. Different Force Metals give different enhancements.

This gets even more powerful with larger Force Metals or those which have been refined repeatedly. But by using larger or more powerful Force Metals it also accelerates the negative side effects.

While Force Metals tended to give increased capabilities for reploids, some had negative effects… Like for elemental based Force Metals, which gave immunity to one element, would often cause the reploid to increase their weakness to another element. (So a reploid might get gain some immunity to fire, but become weaker to water-based attacks in the process.)

Unfortunately, all Force Metals had a hidden flaw (which became widely apparent in 2210 after the rebellion). Overuse (or prolonged use) of them caused reploids to suffer side effects from glitches to even turning maverick.

This inevitably lead to Force Metal use being abandoned as an energy source. Focus was turned to other sources and research. (Though Giga City remained in place and mined other minerals/resources instead.)

Force Metal's discovery date was altered (formerly being in 22XX to 2170) to better fit in the timeline. This was done because it would take time for researchers to locate the fallen meteor, mine some of it and research it enough to present to the government in order to gain funding to even build Giga City to begin with. Plus building a city as large as Giga City wasn't something that would easily be accomplished in even a few years.