im a junior in high school and I know that the summer before senior year is probably the most important.I want to be a bio major or have a career in medicine
which do you think is better or would colleges like to see more?
-a research program at a university
-intern and get paid at a local business
cant you do both? i think its possible 
Research probably makes sense for a bio major. High school “internships” are usually not really very rich experiences. A HS student doesn’t usually have much to offer a business that is helpful in terms of skills & experience. But colleges do know that you might not stick with the major you are considering when you apply. So if you want to do the internship, or can’t get a research gig, or just need the money from the internship, then do it.
Either would be fine. Get the details of what each opportunity would involve and do what excites and interests you the most.