Meta tags have gone back and forth in terms of their usefulness for promoting your site. In the late 90s they were a way for nascent search engines to easily categorize sites, then they were abused for keyword stuffing unrelated to page content and their use waned, but they are back again with three major purposes: Facebook Open Graph, Google Authors and Page titles. These are not necessarily "SEO" purposes, but the goal is ultimately the same: making sure that your site puts its best foot forward to gain new visitors.
Metatag module setup
The basic Metatag module setup is pretty straightforward. Download the latest version from the metatag project page. If you don’t have them already you will need the CTools and Token modules.
Setting up Metatag for Facebook Open Graph
There were a few different things I wanted to achieve with the Facebook Open Graph support. Basically, whenever someone includes our page on Facebook I wanted to make sure that the title, description text, and image that Facebook pulled in were the best possible images. I expect that most of the "liking" will occur on our card landing pages. So, I enabled the "Meta tags: Open Graph" sub-module that is included in the main Metatag module. Then I added a meta tag default for the "Campaign" node type by clicking on the bright "Add a meta tag default" at the top of the page on the page at Administration - Configuration - Search and metadata - Meta tags.