Optimus would be unhappier when Megatron unintentionally took advantage of other desires besides these he was obviously noticing, bit that would be then. Pausing mentally at the grudging irritation, Megatron frowned slightly and then hissed as Optimus set an actual pace and rhythm.

Not bothering with using his lazy energy to thrust up, he merely counteracted the tight, electrifying slide of up and down with little twitches and rolls of his hips when Optimus was on his way up or had just seated himself. The way they fit together, there was no charge only when Optimus wasn't at all seated, and he didn't withdraw that much.

In the middle of that crackling charge being built Megatron hesitated and then plucked up, reluctantly and slowly, what he'd felt on a very personal level when Optimus had literally been plugged in everywhere; desire and need for that utter, absolute feeling of being possessed and the more conscious awareness of unwilling, frustrated acceptance of that.

He angled his helm to give his Prime a sharp, dry glance. Optimus wasn't the only one dealing with something... similar. Even if that was a lot newer for Megatron, and it was old and protoframe-deep since spark ignition for Optimus.