What would happen if an iPhone had no phone service on it?

Would one be able to still use Wi-Fi on it?
I think one could still access the music and apps on there, but I'm curious.

P.S. I do not own an iPhone.

Yes, You will require to borrow a micro SIM from a friend for first boot up and login. Once iPhone is started properly you can return the SIM and enjoy all features( except operator based) over Wi-Fi.

Yes Wi-Fi could still be used and apps & music.