Guys, What makes you possessive over a girl you barely know?

I'm talking to this guy and somehow we got on the topic of other guys (ones I talk/flirt with) and he told me that I don't need to worry about those other guys, he's all I'm gonna need. I laughed it off because well no man tells me what to do but part of me felt drawn to him more so because of that. Anyway, what's the end game? Why would he say that?
SN: We've been talking, no dates, for about 1 month.
Guys, What makes you possessive over a girl you barely know?
Post Opinion