The process where the "Cap structure" (composed of a 7- methylguanosine (m7G) group and associated cap-binding proteins) located at the 5' end of an mRNA molecule, which serves as a "molecular tag" that marks the spot where the 40S ribosomal subunit is recruited and will then scan in a 5' to 3' direction until an AUG codon is encountered in an appropriate sequence context to initiate mRNA translation.