Here's why:

* Electronegativity Difference: The electronegativity difference between carbon (2.55) and lithium (0.98) is relatively large (1.57). This suggests that the bond would be polar with lithium carrying a partial positive charge and carbon a partial negative charge.

* Lithium's Metallic Nature: Lithium is a highly electropositive element, meaning it readily loses its electron to form a positive ion (Li+).

* Structure: The structure of CH3Li suggests an ionic character. It exists as a polymeric structure where lithium ions are coordinated to carbon atoms.

* Reactivity: CH3Li is a strong base and nucleophile. Its reactivity is consistent with the presence of a highly polar or ionic bond.

However, the bond between carbon and lithium in CH3Li also has a covalent character due to:

* Electron Sharing: While the bond is primarily ionic, there is some degree of electron sharing between carbon and lithium.

* Bond Strength: The bond is relatively strong, which is not typically observed in purely ionic bonds.

Therefore, CH3Li is best described as an ionic compound with a significant covalent character.