马上【mǎshàng】

马上 goes before the verb and says the action happens right away, or in a moment. 就 often follows it with no change in meaning.

马上 counts from the speaker's point of view. It can cover a few seconds or a few days, as long as it feels close.

Telling what happened next

In a story, 马上 says one thing followed another at once.

Before the verb, not at the end

"Right away" and "at once" sit at the end in English. 马上 goes before the verb.

• × 我来马上 → 我马上来
• × 你回家马上吧 → 你马上回家吧

马上就要…了 for "about to" overlaps with 就要…了, which has its own point.