The Milky Way had two meanings in the Men in Black series.
One was an energy source, subatomic energy from the universe capable of easily destroying a planet—the marble pendant Russell held in his hand.
The cosmic civilization known as the Akilene Empire possessed one Milky Way. Because of its immense power, they dared not store it within their homeland, so a royal-born custodian hid it on Earth and entrusted it to a cat.
Unfortunately, the Acquilonians went to war with the Bugs, and a Bug spy stole this crucial intelligence before heading to Earth in search of the interstellar weapon.
The plot of Men in Black began around this Milky Way, with Earth, as a neutral party, unfortunately becoming embroiled in the war between the Acquilonians and the Bugs.
The Milky Way's second meaning was simply a celestial system, one of the structures that made up the universe.
The two meanings were worlds apart, yet they did not conflict within the worldview of Men in Black, because at the end of the story, the Milky Way containing Earth was hidden inside an alien's marble.
One man's leaf was another man's universe; one man's ant was another man's god!
Whether it was a marble or a locker, they conveyed the same idea.
Worlds were nested layer upon layer, and the universe was endless. This world was vast, and humanity had no reason to be smug over its little achievements.
Russell looked at the marble in his hand, wondering whether there truly was a galaxy inside. He raised it and waved it at the surveillance camera, then took it away together with the Orange Cat.
Taking the initiative to approach the Men in Black was out of the question. That would be beneath him. He was a man of status; they