Metal alkyl complexes are prepared generally by two pathways, use of alkyl nucleophiles and use of alkyl electrophiles. Nucleophilic sources of alkyl ligands include Grignard reagents and organolithium compounds.  Since many strong nucleophiles are also potent reductants, mildly nucleophilic alkylating agents are sometimes employed to avoid redox reactions.  Organozinc compounds and organoaluminium compounds are such milder reagents.
Electrophilic alkylation commonly starts with low valence metal complexes.  Typical electrophilic reagents are alkyl halides.  Illustrative is the preparation of the methyl derivative of cyclopentadienyliron dicarbonyl anion:
:CpFe(CO)Na + CHI → CpFe(CO)CH + NaI
Many metal alkyls are prepared by oxidative addition:  
An example is the reaction of a Vaska's complex with methyl iodide.