これは鉛のように重い。

this (indicating an item near the speaker, the action of the speaker, or the current topic); this person (usu. indicating someone in one's in-group); now; here; I (me); certainly

topic marker particle; indicates contrast with another option (stated or unstated); adds emphasis

lead (Pb)

indicates possessive; nominalizes verbs and adjectives; substitutes for "ga" in subordinate phrases; (at sentence-end, falling tone) indicates a confident conclusion; (at sentence-end) indicates emotional emphasis; (at sentence-end, rising tone) indicates question

in order to (e.g. meet goal); so that; take care (so as); hoping or wishing for something

heavy; weighty; massive; heavy (feeling); depressed; gloomy; blue; uneasy; slow; sluggish; lumbering; ponderous; clumsy; important; serious; grave; serious; severe; critical; solid; established; dignified; sensible