Typically, lunch boxes are associated with food items that are either dry or meant to be kept cool. But, the insulation that is present in them, will also allow you to store hot meals inside of them. Just know, it will be a little harder to maintain than colder food will. To start, right before you place your meal into the lunch box, either microwave it or place it in the oven to raise the temperature. Then, wrap it with aluminum foil and then place it inside the lunch box. If you plan on leaving the contents in there for several hours, it may not be scorching hot but it should still be warm.
Of course, you also need to remember you may not be able to keep cold contents with warm ones. If you have any sort of ice inside, it will be twice as difficult to store hot foods. Your best bet is to avoid as many hot meals as possible, although if you devote your pack to it, you would be fine.