* "Discovery" is complex: The "discovery" of a metal can be gradual, with different civilizations recognizing its properties at different times. For example, gold was likely known and used in prehistory, but its scientific understanding developed much later.
* Accessibility matters: The abundance of a metal doesn't always mean it was the first to be "discovered." Some metals, while common, are difficult to extract from their ores. This is why metals like iron, though abundant, were likely used much later than metals like gold or copper, which are found in a more easily usable form.
* "Common" is relative: It depends on what you mean by "common." The most abundant element in Earth's crust is oxygen, but it's not a metal. If you are talking about the most abundant *metals* in the Earth's crust, then it would be aluminum. But aluminum was only isolated in 1825 because it's so difficult to extract from its ore.
Therefore, it's not entirely accurate to say the most common metals in the Earth's crust were discovered first. While abundance plays a role, the ease of extraction and historical context are equally important factors in the timeline of metal discovery.
