As said, unfortunately, you can't on a stock iPhone, nor are there apps to do it because Apple believes that would equal piracy by downloading music on one iTunes account and ripping and sharing it to others. Not saying your intentions is piracy, just that that's Apple's mentality.
You can view mp3 attached files, just that you can't physically send them without having root access to your device, which is the case for Android base devices by default
Sent from my iPhone using Tapatalk 