Binary programs are executed on the CPU but the program file is an archive with sections, and only one of them is the program, usually, while the others are all metadata. The CPU isn't capable of understanding the program file at all. Linux has to establish the conditions under which the program runs, that means at a minimum establishing the address space in which the program counter lies then jumping to that address. The instructions for how to do that are in the metadata sections of the ELF executable.