Macros in Elixir allow developers to write code that generates code at compile time, enabling metaprogramming capabilities and enhancing the expressiveness of the language.

Macros are a powerful feature in Elixir that enable developers to perform metaprogramming, which is the practice of writing code that can generate or transform other code at compile time. By leveraging macros, developers can create reusable code patterns, enhance expressiveness, and reduce boilerplate in their applications. In Elixir, you define a macro using the defmacro keyword, similar to defining a function. When a macro is invoked, it receives the code as an abstract syntax tree (AST), which it can manipulate before the code is compiled. This allows you to introduce domain-specific language (DSL) features or optimize repetitive code patterns. For example, you might create a macro that defines a set of validations for a data structure, allowing you to write concise and readable code without duplicating logic. One of the key advantages of macros is that they are expanded at compile time, meaning the generated code becomes part of the module where the macro is called, rather than being executed at runtime. This can lead to performance improvements and more predictable behavior. However, because macros operate at the syntactic level, they can make code harder to understand if overused. By using macros judiciously, Elixir developers can create more expressive and maintainable applications that leverage the language's unique capabilities.