What it does
I'm not aware of "First Contact" as an official Magic: The Gathering keyword or ability. It doesn't appear in any current rules set or card mechanic that I can verify.
It's possible you're thinking of a card name, a custom/homebrew mechanic, an ability from a different game, or perhaps a misremembered keyword. There are similar-sounding mechanics—like "Cohort," "Skirmisher," or various "enters the battlefield" triggers—but none called "First Contact."
If you can share the specific card or where you encountered this term, I can give you an accurate explanation. I'd rather tell you I don't recognize it than invent rules text that could mislead you during a game—especially in Commander, where rules interactions across multiple players matter a lot.
