I would suggest you major in the Biological Sciences with perhaps a minor in chemistry. Having said that, if you have an area of interest, such as history, language, sports; try and make an effort to explore these other area of interests. Medical Schools like to see a degree of diversity. They would prefer to see a person who has interests, which will expand their personality making for a more rounded professional.
Before applying to Medical Schools, talk to your councilors. They may be able to give you some very beneficial suggestions as to where to apply, and based on their knowledge of your interest and abilities what courses to take.
Pick a major that interests you so you don't mind devoting a majority of your hours to studying. You will need to get good grades in college in order to apply for medical school. At the medical school I attended, the average GPA is reported to be 3.85, so even one or two B's can hurt your chances of acceptance.
Aside from this, any major is acceptable as long as you complete the prerequisite courses. I chose to major in biochemistry because there was overlap with the premed requirements and I wanted to complete my degree in 3 years.
Typical medical school prerequisites include:
Biology: Lecture – 4 semesters; Lab – 1 semester
General Chemistry: Lecture – 2 semesters; Lab – 1 semester
Organic Chemistry: Lecture – 2 semesters; Lab – 1 semester
Biochemistry: Lecture – 1 semester
General Physics: Lecture – 2 semesters; Lab – 1 semester
Math: Statistics – 1 semester
English: Rhetoric (Composition) and Literature – 2 semesters