Copper and other commodities opened the week sharply lower as the dollar gained steam against main currencies, ahead of the Fed Chair Janet Yellen's speech in Friday in Jakson Hill, at which she might signal a rate hike soon.

Copper futures tumbled 1.15% to $2.142 a pound, after hitting a one-week trough at $2.135, while gold futures slid 0.60% to trade at $1,338 an ounce. Silver slumped 1.81% to hover around $18.96 an ounce.

The dollar advanced 0.21% against a basket of six major peers to 94.69, while gaining 0.50% on the yen to trade at 100.70, after dropping below 100 last week.

Crude prices also slumped today alongside other commodities, with Brent crude futures down 82 cents, or 1.63% to $50.05 a barrel, while U.S. crude futures plummeted 74 cents, or 1.51% to hover around $48.36 a barrel.

There's not much data today from around the world, with Canada's wholesale sales expected to have risen 0.5% m/m in June, slowing down sharply from May's 1.8% growth, which could weigh on the loonie.