I just wanna say too:

I watched a behind the story thing with 'why they did joker the way they did' thing with Suicide Squad and they said, for example, his metal teeth were there because it was supposed to be 'carry over' (or something like that) from the comics (or one of the animations) where Batman knocks Joker's teeth out for killing Robin. Now look, if you are a hardcore fan, maybe you got the reference. I prefer marvel but I'd like to consider myself a bit knowledgeable on DC characters. There is no way I would have known that was why Leto's Joker's teeth were metal. Unless you knew that going into the movie, it made no sense. And even if you DID know that, it still makes no sense because there is barely a reference to it and has nothing to do with the movie (no tie in, NOTHIN! just the assumption everyone knows the background like it's supposed to be common sense. Hell, i didn't even know there was an arc where Robin died). Supposedly, it's hinted at during the character openers, iirc it's under Harley's "killed robin".