Plugins are likely one of the most powerful features of Magento. They allow us to modify the behavior of public class functions by intercepting a function call and running code before, after, or around that function call.

Before we eagerly start using them, it is worth emphasizing how plugins can't be used on the following:

• Final methods
• Final classes
• Non-public methods
• Class methods (such as static methods)
• __construct
• Virtual types
• Objects that are instantiated before Magento or FrameworkInterception is bootstrapped

Plugins can be used on the following:

• Classes
• Interfaces
• Abstract classes
• Parent classes

By doing a lookup for the <plugin string across the entire <MAGENTO_DIR> directory's di.xml files, we can see hundreds of plugin examples spread across the majority of Magento's modules.