What happens if a male cum in another males anus? and can it spread stds ? (should i use condoms?

The transfer of sexual fluids also transfers any germs (STD's) contained in those fluids. Condoms provide some but not complete protection against a variety of STD's. If you are sexually active, getting screened for STD's every so often is part of a good practice.

Anytime one has unprotected sex, he or she is vulnerable to STD'S and HIV. Always use a condom ,and know your partners history. Safe sex is the best sex.