Moses went to receive the Ten Commandments. When he returned he found the Israelites worshiping a golden calf. 

Was it the calf’s fault?
Further down the road poisonous snakes began to bite the Israelites. God had Moses to make a brass snake to look at when they needed a healing. Did the snake heal them? 
The molten animals weren’t responsible for the Israelites’ sin or the grace they found. Instead they were what the Lord used to reveal their hearts. The worshiping of the calf showed that they were unfaithful to God. The willingness to look at the brass serpent showed that they were ready to do whatever God commanded. 
We can see the reflections of our heart based on actions we take in our daily walks. He is willing to use things or those around us to help us to grow. 
Scripture taken from: Numbers 21: 8-9