Can you put a form in a modal?
You can place the Login and Signup form right in the same Modal. This way, the user triggers the modal, then can either login or register right from that modal. Another way you might try this is to simply provide links to both the Login and Signup pages of your website in the Modal.
What is modal Bootstrap?
Modals are built with HTML, CSS, and JavaScript. They're positioned over everything else in the document and remove scroll from the <body> so that modal content scrolls instead. Clicking on the modal “backdrop” will automatically close the modal. Bootstrap only supports one modal window at a time.