Currencies are moved by many factors, including supply and demand, politics, speculation and economic growth.
Typically , there is an inverse relationship between the value of the dollar and commodity prices.
When the dollar strengthens against other major currencies, the prices of commodities tend to drop.
When the value of the dollar weakens against other major currencies ,the prices of commodities generally move higher.
When raw material prices rise, demand tends to fall. Conversely, dollar weakness the price of raw materials tend to fall in other currencies and lower prices tend to increase demand. This is why the dollar has such an important role in influencing the price of commodities.