Blood
"Blood is thicker than water," the sleazy official had sharply stated in the meeting when Sam's intense loyalty to his alien friends was put under scrutiny.
Except, that wasn't true, and Sam knew it. He was far closer to the Autobots, beings from another planet, than he was to the majority of the members of his own human family.
"Then I must have Energon running through my veins," Sam had retorted, "Because I would rather stand with them than by you."