Kre-Ons have feet compatible with Legos. Minimates have feet compatible with Legos. Therefore, Kre-Ons can use the same accessories that Minimates use, which is why Megatron is now possessed by the Phoenix Force.
The matrix they're mentioning is, of course, the Autobot Matrix of Leadership. It does something different in every continuity, but Megatron always wants it. Or at least, he used to.
And if you've never read any X-Men comics, "I am life and fire incarnate" is Phoenix's catchphrase.