Left-invariant differential form

Let $G$ be a Lie group, and for $a \in G$ let $L_{a} : G \to G$ denote left multiplication. A differential form $θ$ is called left-invariant if for every $g \in G$

L_{a}^{*} (θ_{g}) = θ_{a^{- 1} g} .

The standard example is the MC form.