<menu>
A list of commands — semantically a ul whose items are interactive controls.
Baseline: Widely available · Grouping content
When to use it
For toolbars and command palettes where each item is a button or action link.
When not to
Not for navigation menus (that's nav with a ul) — menu means 'things you do', not 'places you go'.
Example
<menu>
<li><button type='button'>Copy</button></li>
<li><button type='button'>Share</button></li>
</menu>