He was a CS major. And he made it very obvious in his application. I’d pretty much say his essays were “I’m a computer nerd. Take me or leave me.” It’s not particularly an approach I’d recommend, but it worked for him as a very one sided kid. (Except for also being a huge reader, for Harvard he gave him his year long reading list as the optional info - it was mostly sci fi and fantasy, but also a fair amount of computer theory and practical stuff.)
Pre-med is not a major. If you think you are interested you can do medical related volunteering or research. Or you can do what you like. Some of the nicest pre-meds I knew were music majors. No med school is going to care about what you did in high school.