What will happen if I put my LG sim card into my iPhone 4s?

I got and iphone 4s and i still have my lg motion touch screen connected to metro pcs. Yesterday i went to metro pcs and asked if they have a connection (sim card) iPhone ones and they said yes, (they released a new connection " two days ago". Anyways i want to put in my sim card from my lg phone to my iPhone. Can I do that? Will it delete my contacts or pictures or just information from my lg? Please answer simply but in a lot of detail!

If both cards are dimensionally the same, go for it. You will run into a problem if the SIM card is for a different phone company, but it won't erase any of your vital data. You should be able to look at a friends pictures and music that way though, Right?