The earliest instance so far discovered of magical metal bending is “Ireland's Famous Bent Penny” in Ireland's Magic Hand Book and Catalog by Laurie Ireland and Carleton King, 1932, p. 11. Ireland's trick was presented as a gag in which a spectator supposedly squeezes the performer's fist too firmly, causing a penny inside to bend rather than disappear.
“Atomic Penny” in Ben Berger's Highlight Magic, 1941, p. 11, takes the feat of a bending penny into a spectator's hand, which is the comedy climax of a multiphase routine in which the size of a penny waxes and wanes.
The gag where a spoon is apparently bent by pressing it against a tabletop was described but not explained in a Denver, CO, IBM Ring report in The Linking Ring, Vol. 10 No. 3, Apr. 1930, p. 327. The reporter wrote: “Perhaps most of our readers will be familiar with this little gag, but it was new to us[…]” An explanation appeared, using a fork instead of a spoon, in Bert Douglas's “Magic for Men” column in The Linking Ring, Vol. 13 No. 9, Nov. 1933, p. 641. Sid Lorraine taught the more common version using a spoon in Tops, Vol. 9 No. 6, June 1944, p. 8. Lorraine writes: “I believe, by the way, that I was one of the first to introduce this among American Magicians…I showed it at a S. A. M. gathering in Chicago about 1930 or '31…It had been shown to me by a Toronto trixter who picked it up from a non-wizard.” Lorraine's dates fall after the mention in the Denver Ring report, suggesting the trick was circulating elsewhere in or before early 1930. The convincer of using a nickel to substitute as the end of the spoon handle was added by Nepomuk (pen name of David Verner, one of Dai Vernon's sons) in “Nickleplated”, published in The Phoenix, No. 200, Apr. 7, 1950, p. 799.
The gag based on an optical illusion in which a pocket watch, or large coin is apparently bent by flexing the hands back and forth is described as having been taught by Robert Hellis to a student, c. 1873, in Hellis in Wonderland, ed. and published by Will Houstoun, 2010, p 97-9. However, its earliest publication is thought to be in Tricks, Vol. 1 No. 2, June 15, 1901, p. 15.
Metal bending as a serious “psychic” feat was established in the early 1970s by Uri Geller, who appeared to bend keys and silverware by sheer concentration. Geller seems to have been the first to present the effect of bending keys. In the International Herald Tribune, Apr. 9 1991, James Randi claimed Geller's feats “are the kind that used to be on the back of cereal boxes when [Randi] was a kid.” This may have just been a disparaging remark about the quality of Geller's methods rather than suggesting the exact mechanics had been taught on food items in eras past, but this remains uncertain.
Theodore Annemann's “Bending Swizzle Stick”, although the stick is made of glass, is often recognized as an early relative to nail and spoon bending; see The Jinx, No. 3, Dec. 1934, unnumbered third page.