Metro5 is fairly straightforward in that it's an engine that just searches the web or news. It then displays the top 50 results that it finds in a basic text format. The unique point that it has is that you as the searcher can rate a site, by saying that you like it or dislike it, and 6 different reasons why that may be the case. Your ranking is confirmed by tweeting the rank for everyone that you follow to see. That's what makes this one interesting, since you could easily set up a filter and/or edit your tweet to allow other people to follow it. It would be great at a conference for example if someone was able to do that - of course you could just tweet it, but this is a nice simple way of doing that for you.
However, other than that, it's a very basic engine with the usual search functionality that you could expect.