Can I use my regular 3.5 mm earphones with an iPhone? The earphones that I have received with my iPhone have 4 metal connector jack. By the size of it, it looks 3.5 mm in diameter. Unfortunately, the white earphones are not of the in-ear type and slip out from my ears quite frequently.

I have a different set of Sony earphones with a 3.5 mm jack. It has 3 metal connectors which means that if I insert it in the iPhone, at least I am shorting out 2 metals receptors on the iPhone female. Is it fine to do such a thing? My guess is that if the short is occurring between the mic and the ground, it should be fine as usually not a lot of current is sourced to a mic. I was just looking around for more information. A connection diagram would be great.
Yes, you can use any earphones with a 3.5mm audio jack. I'm surprised you did not just try it out :)

I thought I'd add some additional background information I just read about in a report on yet another Apple-Samsung patent case, Apple holds a patent on an audio jack which has the circuitry to detect the type of headphones plugged in, and I can only assume this is what they actually use in their iPhones.