Meaning "direction given by example" (as in follow (someone's) lead) is by 1863, that of "a clue to a solution" is by 1851, both from the notion of "thing to be followed." As an adjective, "leading," by 1846. Lead-time "time needed to produce something" is 1945, American English.
"to guide," Old English lædan (transitive) "cause to go with oneself; march at the head of, go before as a guide, accompany and show the way; carry on; sprout forth, bring forth; pass (one's life)," causative of liðan "to travel," from Proto-Germanic *laidjanan (source also of Old Saxon lithan, Old Norse liða "to go," Old High German ga-lidan "to travel," Gothic ga-leiþan "to go"), from PIE *leit- (2) "to go forth."
Of roads, c. 1200. Meaning "to be in first place" is from late 14c. Intransitive sense, "act the part of a leader," is from 1570s. Sense in card playing, "to commence a round or trick," is from 1670s. Meaning "take the directing part in a musical performance or prayer" is from 1849. Related: Led; leading.
To lead with one's chin "leave oneself vulnerable in a contest" (1946) is a figure from boxing. To lead on "entice to advance" is from 1590s. To figuratively lead (someone) by the nose "guide by persuasion" is from 1580s, from draught animals (earlier lead by the sleeve, early 15c.). To lead (someone) a dance "compel through a course of irksome actions" is from 1520s.
heavy metal, Old English lead "lead, leaden vessel," from West Germanic *lauda- (source also of Old Frisian lad, Middle Dutch loot, Dutch lood "lead," German Lot "weight, plummet"), a word of uncertain origin. The name and the skill in using the metal seem to have been borrowed from the Celts (compare Old Irish luaide).
Figurative of heaviness at least since early 14c. American English slang lead balloon "dismal failure" attested by 1957, perhaps 1940s (as a type of something heavy that can be kept up only with effort, from 1904). Lead-footed "slow" is from 1896; opposite sense of "fast" emerged 1940s in trucker's jargon, from notion of a foot heavy on the gas pedal.
Meaning "graphite in a pencil" is from 1816 (see pencil (n.)). Black lead was an old name for "graphite," hence lead pencil (1680s) and the colloquial figurative phrase to have lead in one's pencil "be possessed of (especially male sexual) vigor," attested by 1902. White lead (1560s) was an old name for "tin."
As a name of a dull bluish-gray color, 1610s. From 1590s as figurative for "bullets." Lead oxide was much used in glazing, mirror-making, and pigments. In printing, "thin strip of type-metal (often lead but sometimes brass) used in composition to separate lines" from 1808, earlier space-line. Lead-poisoning is from 1848; earlier lead-distemper (1774).