“一马当先”，汉语成语，意思是原指作战时策马冲锋在前（gallop at the head）。形容领先，积极带头。可以翻译为“take the lead，be in the forefront”等。

例句：

他干什么活儿都是一马当先。

He takes the lead in whatever work we do.

不管任务多么艰巨，他总是一马当先，挑起重担。

However difficult the task is,he is always the first to shoulder heavy responsibilities.