I’ve used as a binder. I put it in most all my marinades. But straight up on a steak? Never have I. I’ll give it a go.
Mustard as a binder is classic in bbq. Also, it's how to make an in-n-out burger animal style (like a binder before pan frying). It sort of creates a carmalized crust.
Also, mustard is a classic condiment for roast beef, corned beef, and pastrami (not to mention an all beef hot dog).
To clarify my initial response, I prefer Plochmans yellow mustard due to the appropriate vinegar flavor. French's just doesn't do it for me (not enough zip).
Guldens has a great brown mustard flavor that is balanced while others can be gritty or bland. Duesseldorf mustard has a great universal balance.
Colemans and Chinese mustard have the nasal heat that pairs well with certain dishes and clears the sinuses (recommended over horseradish mustard although prepared horseradish and horsey sauce have their place).