There are many reasons why people test their soil. One is to get a snapshot of the minerals and nutrients in the soil. If you have a house that was built before the 1970s, you may want to make sure that soil near the house is lead-free.
You can get your soil tested, including a test for heavy metals, easily and inexpensively by taking a sample and sending it with a check for $9 to the University of Massachusetts at Amherst. Here are some overviews on how to take a sample.