What do you need to connect copper to galvanized pipe?

Yes. Use a threaded fitting, male or female as needed on the copper and screw the galvanized into it.

You must use a dielectric fitting to connect copper to galvanized pipe. If you don't, a galvanic reaction will occur and the piping will corrode and leak. You can use a Dielectric Union or a Threaded Brass fitting to join the two types of piping together.

UNIONS can leak the best answer would have been a dielectric nipple