Syntheses and reactions of organometallic compounds having Si-Mtl bond as well as “metal free” silyl anion species are reviewed in the order of the periodic classification of metal elements. With these reagents, silyl groups are successfully introduced into organic substrates by (1) substitution of halogen of alkyl, allyl, aryl, vinyl, and acyl halides, (2) addition to ketone and aldehyde carbonyls, and (3) addition to alkynes, allenes, and conjugated dienes. These reactions are useful for synthesis of versatile organosilicon compounds.