Modal verbs, which express a likelihood, ability, permission, request, order etc., usually help main verbs to state the future. It is the reason they are categorised as auxiliary verbs in the context.

The simple future tense in French is used to express ‘I will + verb’ in English. Nous mangerons au restaurant si tu veux. – We will eat in the restaurant if you want. Elle jouera au foot le week-end ...