Maybe very different meta in different section of the site, have use seo optimizer for that before plone 5.
There are some options:
The best and most flexible way is to register a viewlet for the viewletmanager plone.htmlhead. (See plone.app.layout.viewlets.configure.zcml for example viewlet registrations in plone.htmlhead). That way you can control what to inject quite easily via Python.
If the need to add custom metadata arises only where you also have a custom view, you can inject the metadata from within your view template by using
<meta name="theme-color" content="#ffffff">
Code of Conduct –
Hosting courtesy of Rackspace