These databases are great for 'hot topics'. If your topic is one that is widely debated, chances are you'll find sources supporting both sides in one or more of these!
If you can't find your topic in the databases, you can try a targeted search in Google using terms specific to your topic. Refer to this cheat sheet for some tips!
*Remember, Google will give you access to a wider range of sources than the databases, BUT you will have to:
Determine if a source is credible before you can use is
Generate your own citation (use Purdue OWL's MLA Formatting Guide)