What is the future tense for grills?

There isn't a future tense for "grills" in the same way that there is for verbs. "Grills" is a noun, which doesn't change based on tense.

To express a future action with "grills," you'd use a verb like "grill," "will grill," "are going to grill," etc. For example:

* We will grill hamburgers tomorrow.