In HTML (Hypertext Markup Language), the <meta> tag is used to provide metadata about a document. Metadata is information about the HTML document that is not displayed on the web page but is important for various purposes, such as search engines, browsers, and other web services.

Here are some common metadata elements that are often included in the <head> section of an HTML document:

Document Title (<title>): The <title> element defines the title of the HTML document. It is displayed in the browser's title bar or tab and is often used by search engines to determine the page's content.

html
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Example Page</title>
</head>
<body>
    <!-- The content of the web page goes here -->
</body>
</html>

Character Set (<meta charset>): The <meta charset> element specifies the character encoding for the HTML document. It is important for ensuring that the browser interprets the text content correctly.
```
html
<meta charset="UTF-8">
```
Viewport Settings (<meta name="viewport">): The <meta name="viewport"> element is used to control the viewport properties, such as width and initial scale. It is crucial for creating responsive and mobile-friendly web pages.
```
html
<meta name="viewport" content="width=device-width, initial-scale=1.0">
```
Description (<meta name="description">): The <meta name="description"> element provides a brief description of the document. Search engines often use this description in search results.
```
html
<meta name="description" content="This is an example page with some interesting content.">
```
Keywords (<meta name="keywords">): The <meta name="keywords"> element allows you to specify a list of comma-separated keywords relevant to the content of the page. While not as important for search engines as in the past, some may still consider it.
```
html
<meta name="keywords" content="HTML, CSS, web development, example">
```

Including these metadata elements in the <head> section of your HTML document is essential for providing important information to browsers and search engines, enhancing the accessibility and usability of your web pages. Keep in mind that some metadata elements may have more impact on search engine optimization (SEO) than others. Always follow best practices and stay updated with current web standards.