We can use properties such as electrical conductivity and acid-base character to classify elements as metals or non-metals
Characteristic Properties of Metals and Non-Metals
Metals & Non-Metals in the Periodic Table
The location of the metals and non-metals shows a clear pattern when highlighted on a periodic table
Another thing that is striking, is that you can see that the vast majority of elements are metals
A zig-zag line between the blue and purple elements in this diagram separates the metals on the left, from the non-metals on the right. Elements which border the line are hard to classify as they have characteristics of both sides, so the term semi-metal or metalloid is used.