Transmetallation

Organolithiums can be converted to other organometallics by adding the salt of a less electropositive metal. This typical of organometallics - it isn't restricted to lithium.

This can be useful. For example, in the molecule below, an organolithium deprotonates a proton rather then attacking a carbonyl:

While ethynlcerium dichloride will attack the C=O:

I don't have a good explanation for why some organometallics are more basic while some are more nucleophillic. These properties are found experimentally.