Led and Lead each have multiple meanings, both as verbs and nouns. We’ll primarily focus on the verb forms, since these cause the most confusion. At the end we will review the nouns briefly.
As verbs, led and lead are two different grammatical forms of the same verb, to lead, meaning “to guide or go first.” Lead is the present tense form, rhyming with seed. Led is both the past tense and the past-participle, rhyming with bed:
Jane will lead the group into the jungle. (present tense)
Roberta led them into the ancient temple. (past tense)
Judy has led many tourists on such journeys. (past participle)
Like to lead, most English verbs have the same form in the past tense and past participle; for example, the forms kicked, cooked, and dated. But there are many English verbs with different forms for the past tense versus past participle (pp), such as ride (present), rode (past), ridden (pp) and eat (present), ate (past), eaten (pp). This is because of the mixed Latin/Germanic grammar and vocabulary of English.
Just remember that lead is for the present, and led is for the past and past participle.
Now, as nouns . . .
Lead, when pronounced to rhyme with bed, means:
1. the name of a heavy metal with the chemical symbol Pb
2. a name for the substance inside pencils (which is graphite, not lead (Pb))
Lead, when pronounced to rhyme with seed, means:
1. an insulated wire connected to an electrical device
2. the status or condition of going first: being in the lead
3. the first action of a series, such as the first announcement, first strategy, or first attack
4. a clue to solving a crime or mystery
Led is a noun properly written LED, which is an acronym for light emitting diode. LEDs are the tiny green and red lights that indicate power on many electronic devices.