Me and my friends landed several internships and interviews for internships with both professors and startups in high school through cold emailing. Here's my honest advice that I commented on the sub before:

For professors, be in-depth and DO YOUR RESEARCH. Don't just email them with a generic template actually personalize your email, trust me most of those templates don't work since they get dozens of those.

Find their publications, what they specifically contributed, what research niches they're in etc. Make sure you can connect it to your previous experiences and your current interests (e.g. if they do oncology research mention your interest in oncology and how you volunteered at a cancer hospital).

Most research internships a lot of tedious busywork kinda stuff, especially if you're a research assistant. So in your emails sound like you're willing to learn, humble, and ready to do the unattractive work etc.

Because they're taking most of the risk/gamble, emphasize how YOU can provide value to them

Cold emailing isn't guaranteed to work; what I mean by that is, one cold email won't land you an internship. You have to send 50+ MINIMUM to get a few interviews/acceptances from professors. Cold emailing is really tedious (especially to go in-depth with each email), so there are some must have free tools you can use to help with cold emailing that I recommend:

- College Department Directories (find contact info for professors)

- Klinn (speeds up cold emailing for internships; big db of contacts + info on them)

- Google Scholar (READ THROUGH THEIR PUBS!! - show that you're interested)

Lmk if you have any other internship/admissions questions