What makes a person alluring to you?

What makes a person alluring or attractive to you? I don't necessarily mean the things you look for in a life partner. Rather, what qualities and attributes make someone seem interesting, charming, charismatic in a social situation and make you want to engage with them? Or maybe not even engage with them (because many have social anxieties, of course) but make you feel like you wish you could engage with them. This can mean simply talking to them, wanting to befriend them or join them in conversation, or it could even mean feeling the primal desire to be romantic with them. Not necessarily "what turns you on" in a preference sort of way, but more base and reactionary. Are there qualities that some people possess that you just can't ignore? What makes a person someone you can't help but gravitate toward?

I just want to clarify that I don't necessarily mean this is a romantic sense. I'd love to hear what makes you feel attracted to others in a romantic way, but I also mean in a purely platonic way too. Is there something about a person that makes you feel like you want to know them better?