I spend a lot of my time trying to get my students to sound less formal.

It’s a common problem with English learners. They learn the language but, not having so many opportunities to use English in social settings, tend to gravitate towards more formal, written English, even when they’re speaking.

However, as I always tell them, there is a time and a place for English in the higher registers, something that your students might call more “advanced” structures.
And these things can be fun to learn, too. And what’s more satisfying than being able to show off to people at dinner parties with your flashy new grammar structures?

But, more importantly, perhaps, these kinds of advanced structures are a nifty way to score some extra points in IELTS or TOEFL or CAE.
When I think about these kinds of structures, there are two that come to mind straight away: negative adverbials and inverted conditionals.

Both of these structures have clear rules and immediately make you sound like you read a lot of Dickens.
In this video, I go through the three inverted conditional forms in English: how to make them and how to make them negative.