Chaos Tool Suite is one of the best API module to use. The module mainly provides API.
I've worked on ctools before to create multi-step form and show that in popup. This time I'm working on a project which has a Quiz in it which is built using ctools. The site was having a requirement of displaying Quiz form when user clicks on link from E-Mail.
So to display ctools modal on page load we've to add below jQuery Code: