It's very likely that…

…if you're using javascript:void(0) as the value of the href attribute, the element you're actually looking for is <button>.

<a href="javascript:void(0);">
  Open modal
</a>

More accessible alternative:

<button>
  Open modal
</button>

Explanation

The role of <a> is link and the role of <button> is button. Users have certain expectations when they find an element. A general rule of thumb: Use a link if it takes you somewhere else. Use a button if you submit a form or run JavaScript.