Strength of materials is a way of thinking about how materials like wood, steel, and plastic respond to forces like tension, compression, and bending. When a material is strong, it means that it can resist these forces without breaking or bending too much. So, if you have a bridge made of steel, it can hold up a lot of weight because it is very strong. It can withstand big forces without breaking. On the other hand, if you have a bridge made of paper, it won't be very strong and probably won't be able to hold up much weight.