I'm an incoming M1, but I took an SMP and know many current M1s from the same SMP that are doing veryyyy well based on the classes we took.
Human Genetics, Microbiology, Immunology, Anatomy, Histology, Physiology, Pharmacology, Neurosciences, Pathology, Embryology. All upper level, not intro courses. EDIT: We also had a Medical Ethics course that was pretty interesting.
Obviously, I haven't started M1 yet, but I am sure these courses have laid a pretty strong foundation as they more or less "mimic" med school coursework!