After T0's speech, what if the metal breath was a way to spread the Cardbots' influence all over the universe and control them to form order. As I've said before (a what-if), Deus Machina is a mother computer virus, and they're all parasites.
What if there was more than one Speranza. What if the reason why there are barely any Star Guardians around was that they were on another planet and in the same situation as BC; becoming the bridge of connection between their kind and another.
Gigantrex's mission was to find a home for the 2 billion Cardbots sleeping. A perfect home. One that wouldn't disturb another existing lifeform species (wasn't even necessary, as long as they found a place). Gigantrex dodged a massive nuclear bomb by prioritizing the fact that Earth was humanity's home. They can't just unleash their kind here.
Remember when Deus Machina told BC to "find a friend" through the metal breath.
What if (so many), it was to illustrate the true purpose of the mission: to colonize planets and finally, the entire universe. To establish control and spread their influence. Maybe other than the ongoing war between the Metal and Wild Cardbots; what if the reason why they have so many weapons equipped (cough cough, Blastrain). Was to make it easier.
As a mechanical (and superior) lifeform who could destroy planets and is deemed powerful/ dangerous, their weaponry and physical capabilities that exceeds others are what make gaining control over others a more plausible outcome.
The majority of the Cardbots' response to being sealed or offered an alliance is met with hostility. Because that was a response considered normal to them. Except for others who were on the more peaceful side, those who were strong didn't find violence necessary. And those who were weak knew they weren't strong enough to overpower anyone.
And that's where the metal breath comes into play. Let's look at BC; can't lift a truck; keeps getting thrown around; glorified punching bag. He can't do shit. But give him the metal breath. And later it was passed on to Jun. This. This was intentional.
As they capture more Cardbots together, they form a pact. Or order. Something. By combining strength and fighting together, they could defeat stronger foes and add them to the arsenal. "Find more friends!" = Finding more allies. More allies = more control. That's stage one.
Stage two; colonization. But in their point of view; "Let's find new friends!" / "The more the merrier!" / "There's probably more Cardbots out who (PROBABLY) need our help.... Let's go look for them!" They are unintentionally establishing their existing control in other places as they meet new Cardbots.
Stage three; there is no stage three. They've done it. They have spread their virus. The parasites are everywhere. Life that was undisturbed before has been invaded by a new species.
"Find a friend", Deus Machina said.