Learn Spanish (Spain): La cena está hecha; falta que lleguen los invitados. - Dinner is done; all that's left is for the guests to arrive.

The phrase falta que expresses that an action is pending or required. Because the guests' arrival is something that hasn't happened yet and is just anticipated, Spanish requires the subjunctive mood here.

I usually think of faltar as "to be absent" or "to miss". How does it mean "all that's left" here?

The verb faltar literally means "to be lacking" or "to remain". In this sentence, falta que lleguen literally translates to "it is lacking that they arrive." In English, we naturally express this idea as "all that's left is for them to arrive."

Why is the subject los invitados placed after the verb lleguen?

In Spanish, it is very common to invert the subject and verb with verbs of arrival, appearance, or existence. Putting los invitados at the end puts the focus on the event of arriving, which sounds much more natural to native speakers than que los invitados lleguen.

Why do we use está instead of es for está hecha?

We use estar with a past participle to describe the state resulting from an action. The cooking is finished, so the dinner is currently in a "done" state. If you used es hecha, it would form the passive voice, making it sound like a general statement about how dinner is usually prepared rather than its current ready state.