The Read More Button widget allows you to add a “read more” button below your post or on the block in the archive and create a call-to-action.
Button Type: Choose the type of button whether Text, HTML, or an image.
Link to: Set the link to the button.
By default, it is Post URL and that option allows you to further use the AJAX option to view the post content in a modal.
You can customize the popup background and animation timing and other functions as well.