If you fancy to display images, galleries, videos and other content in a lightbox, Easy FancyBox is a very easy to implement one stop solution. It’s simple to configure, does normally not require you to edit your existing content and is privacy-friendly.
Extract from WordPress.org
Easy FancyBox plugin for WordPress websites gives you a flexible and aesthetic light box solution for just about all media links on your website. Easy FancyBox uses an updated version of the traditional FancyBox jQuery extension and is WP 3+ Multi-Site compatible. After activation, all links to JPG, GIF and PNG images are automatically opened in the FancyBox Mac/Gnome-style lightbox that floats over the web page.
https://wordpress.org/plugins/easy-fancybox/