Learn Swedish: Laget kommer att vinna matchen idag. - The team will win the match today.

We use kommer att because this is a prediction about a future event that we don't have direct control over. If you used ska vinna, it would sound like a promise or a determined plan made by the team itself. Kommer att just means you strongly believe this outcome will happen.

Do I always have to include att in kommer att vinna?

In formal written Swedish, yes, it is the standard rule to include att. However, in spoken or casual Swedish, people very often drop it and just say Laget kommer vinna. It is important to recognize both, but keep att for your writing right now.

Why does the word for team become laget but the word for match becomes matchen?

This happens because they belong to different noun genders. Lag is an ett word (ett lag), so it takes the -et ending to mean the team. Match is an en word (en match), so it takes the -en ending to mean the match.

What form of the verb is vinna here?

It is the infinitive form. After kommer att, you must always use the bare infinitive of the main verb. This is exactly the same rule you learned for other helper verbs like ska, kan, or måste.