In the 1940s was the metal content changed in any US coins due to the war effort?

From mid 1942 to 1945, so-called "Wartime" composition nickels were created. These coins are 56% copper, 35% silver and 9% manganese. The only other U.S. coins to use manganese are the Sacagawea and presidential dollars. These coins are usually a bit darker than regular nickels, said to be due to their manganese content (as was true of many British coins minted from 1920 through 1947). However, carefully-protected proof sets of these coins are difficult to tell from the standard alloy. A more likely reason for the darker appearance of the wartime coin was due to exposure to sulfur during circulation, which invariably gave the coins a mild and somewhat distinctive dark silver tarnish.

https://en.wikipedia.org/wiki/Nickel_(United_States_coin)

Yes. Pennies and Nickels.

"Nickels minted from 1942-1945 during WWII contain 35% silver, as the nickel was used for the war effort. Their metallic value is in line with current precious metal prices, as well as the base nickel value. The metal content of these "war nickels" as of April 25, 2007 is worth $0.77."

https://en.wikipedia.org/wiki/Nickel_(United_States_coin)


"Due to wartime needs of copper for use in ammunition and other military equipment during World War II, the US Mint researched various ways to limit dependence and meet conservation goals on copper usage. After trying out several substitutes (ranging from other metals to plastics) to replace the then-standard bronze alloy, it was minted in zinc-coated steel. It was made at all three mints, Philadelphia, Denver, and San Francisco. Coins from the latter two sites have respectively "D" and "S" mintmarks below the date.

However, problems began to arise from the mintage. Freshly minted, they were often mistaken for dimes. Magnets in penny vending machines, placed to pick up steel slugs, also picked up the legitimate steel cents. Because the galvanization process didn't cover the edges of the coins, sweat would quickly rust the metal, turning the coins into a rusty mess. After public outcry, the Mint developed a process where salvaged brass shellcasings were augmented with pure copper to produce an alloy near the pre-war specifications."

https://en.wikipedia.org/wiki/1943_steel_cent