They won't make your site instantly popular. What they will do is provide some search engines the information they need to correctly categorize, describe, and rank your site. Not all search engines use them, but many do. We'll take a look at the most important ones here. Every page on your site needs META tags.
Most search engines use what is called a spider.
A spider is a program that scans and indexes a web page, harvests the links from the page, follows the links to new pages, and starts all over again. Since a spider will index every page on a site, every page needs META tags. Title OK, the title tag is not a META tag, but I can't believe how many sites I visit that don't have a title. The title is what shows up in the title bar of the visitor's browser. It is also what search engines use for the title of your site when they list it.