A recipe for scones in today's Baltimore Sun (warning: pay wall) includes the words "Tips: I always use aluminum-free baking powder because I don't like the idea of eating metal."
Metals are actually a necessary component of your diet to maintain good health. This concept is in fact so important that it's what we cover in the very first lecture of the Metabolism course for first-year medical students (here at what U.S. News & World Report considers the second-best medical school in the United States). Calcium, potassium, and sodium maintain important membrane potentials, and magnesium, iron, zinc, manganese, copper, molybdenum, and selenium are required at the active sites of important enzymes, where they bind substrates, transfer electrons, withdraw electrons, or maintain enzyme conformation.
It's true that aluminum is not on this list (so far!), so if you want to avoid eating it, that's just fine: but please don't avoid it just because it's a "metal". (Or, heaven forfend, a "chemical".)