Copper prices tumbled today to a six-day low as Chinese shares gave up ground along with other Asian markets, while noting that China is the world's largest metals consumer, but undergoing a current economic transformation from manufacturing and investment to consumer spending, which affects copper negatively.

Copper futures fell 0.75% to hover around $2.236 a pound, compared to the previous close price of $2.254, with a session-high at $2.265, and a low at $2.232. Prices hit a one-month peak last week at $2.292 a pound.

China's Shanghai index on the other hand tumbled over half a percentage point before paring losses to register a 0.29% loss, while Japan's Nikkei index skidded 0.49% to trade at 17,353. Australian shares dropped 0.30% after a holiday yesterday.

Oil prices recorded some modest losses ahead of U.S. inventory data later, with Brent crude futures down nine cents, or 0.19% to trade at $44.26 a barrel, while U.S. West Texas Intermediate (WTI) crude futures eased seven cents, or 0.20% to hover around $42.60 a barrel.

Investors wait for an array of data today, with U.S. Durable Goods Orders expected to have risen comfortably in March by 1.9% m/m, compared to February's dismal 3.0% tumble, which would be positive for the dollar.

Also from the U.S., Flash Services PMI for April is expected to climb to 52.3 from March's 51.3, another positive sign for the world's largest economy ahead of the Fed meeting that begins later today.