All the functionality of the product works in Lightning. In fact: most new features are Lightning first (although they still work in Classic).

If you are running version 1.14 you may need to upgrade to a later version of the product to get full Lightning support.

If you need to stay on 1.14 you can also install an unmanaged package that includes support for an alternate implementation of the list view buttons, as well as layout optimizations for Lightning. To learn more, see this article.