There are following meta tag types - title, description, keyword and robots attribute.
When thinking about Meta tags (Meta title and Meta description) let’s do not forget about “Mobile First World”. Since last year there are two SERPs: mobile and desktop. As a result, Google extended amount of characters for mobile devices.
For Mobile: title should be up to 78 characters and description - up to 300 characters.
For Desktop: title should be up to 70 characters and description up to 300 characters.
So if you are targeting mobile users - try to write longer titles.