Not all grains are equal. They each have their own personality. Most people have decided oatmeal is a good thing to eat for breakfast and never branch out beyond that. Oats though are sticky, heavy and warming. Great for wintertime or a cold thin person who wants to gain some weight. I love oats added to a cookie batter or used as a binder for something like a lentil loaf but if I wanted to lose a few inches I'd choose something else for that first meal of the day.
Millet is the only alkalizing grain and has a lovely flavor. I only like it cooked with extra water though or else I find it dry. Using millet like polenta gives you more nutrition than the corn flour product and it is tolerated better by those with intestinal issues. Cous cous is another one that people confuse with whole grains. It is really more of a pasta than a grain which is why it cooks in just five minutes. Better to use quinoa and get a power protein packed whole food than just a convenient filler.
Jobs tears barley is a grass not a grain because it only has one layer instead of three but it cools and reduces inflammation and pain, has anticancer properties and can strengthen the spleen, pancreas and stomach.
Brown rice is the most ubiquitous and bonds to toxins perhaps better than any other grain and carries them out of the body. It also can be cooked in so many ways or eaten plain or as pudding or breakfast cereal. Just eat the cooked variety for the full benefits rather than rice crispies or chips...