The past tense and past participle of the verb lead (pronounced "leed") is led (pronounced exactly as it is spelled).  However, many people write such incorrect sentences as these:  "In the past, I lead a very sheltered life," "During the Civil War, Robert E. Lee lead the Southern armies," and "I am sorry to say that I have lead many an innocent young lady into temptation."  In all three, the correct verb is led.

The "lead" that is pronounced "led" (a homophone of the verb led – i.e., with the same sound but different meaning) refers to a metal and is used as a noun (It is made of lead) or an adjective (We use lead pipes).