Is it a good idea to have forms in a dialog/modal lightbox?

1. When not to use modals?
2. When a modal box appears what should the user do?
3. What makes a good modal?
4. What is the difference between dialog and modal?

When not to use modals?

5. Do not use modal dialogs for nonessential information that is not related to the current user flow. As discussed above, modal dialogs have numerous disadvantages and costs to users. In order for these costs to be justified, their relevance to the task and importance should be high.

When a modal box appears what should the user do?

The purpose of modals can be summed up in one word: focus. If you need visitors to focus on something simple, a modal window is one of the most effective means to do so. Users must either close the modal, or complete a specific action within it (e.g., reading a message and clicking “OK”, filling out a form, etc.).

What makes a good modal?

Having a clear and descriptive message will explain the window's usage. Users should be able to read the text and understand the message you're trying to tell them and possible actions. Try to match the primary button text with the modal window title because it makes it easier for users to understand the context.

What is the difference between dialog and modal?

For example, you could have a dialogue containing a contact form or some text to confirm an action. Dialogues can be included in a modal. This would mean that the modal prevents interaction with the page while the dialogue provides a means to dismiss the dialogue and modal once interacted with.