Does Marketo have a way to show a form that appears over the page as a modal window? Or would it be better to integrate with a service like OptinMonster.
If that's the only thing you want to do a modal for, and you don't want to do a crazy amount of custom work, I'd suggest something like OptInMonster or SumoMe. RTP can do it, but at like 100x the cost of cheaper solutions.
This would be custom so a solution like optinmonster would make it easier
I don't really understand why the others answered the way they did.
Marketo Forms have built-in modal capability. In one line:
MktoForms2.whenReady(function(form) { MktoForms2.lightbox(form).show() })
I completely disagree with just switching to OpenMonster or SumoMe. Those services will not associate leads by default. If you want 3rd-party forms that are actually as useful as Marketo forms, and do not have rate limits, you will need to invest in custom development.