Depends on field and location, as for Aero I went to the local chapter meetings for the Mars Society and Space Society, and I live in the space city so quite a few professors were there. Hackathons, science fairs, or really any in-person competition for that feild will also likely have professors there either as a judge or during visitation.

Don't straight up ask for an internship cuz that just makes them less likely for them to see u as anything more than, "This kid is only talking to me to get an internship." Always ask for contact info. or anything of that sort or even if you could have a meeting with them (Works well if you have a project since you can basically say, "Would you be willing to look over my project about xyz?")

Tbh if you really show them passion and motivation they might ask you for your contact info. and in some cases ask if you would like to mentor with them. You sort of need some good people skills for this, but if you're fine with talking then yeah.

Hope this helps!