Organolithims and Grignard reagents

MO of MeLi:

Both this and Grignards reagents (RMgBr) have their electrons directed towards the oxygen, and they both react as if they disassociate into carbanions.

Grignard reagents are made by reacting magnesium pieces with organic halides:

Ethers are one of the only ways of dissolving Grignard reagents, they stabilize it by co-ordinating lone pairs onto the Mg:

Magnesium filings have a thin surface of MgO. This can be dislodged using ultrasound, or by adding a drop of iodine or 1,2-diiodoethane.

Organolithiums are also made by mixing the pure metal with an organic halide, and they mostly use ether solvents. The difference is that Li doesn't insert, it replaces the halide:

These organometallics are very strong bases and nucleophiles. They need to be kept free of moisture - including vapor in the air. They will react with water rapidly and exothermically to produce a hydrocarbon and a metal hydroxide. 

Anything which can protonate them will do the same thing, but obviously with a different salt: