来月 is a time expression meaning next month, and with this kind of relative time word, Japanese often uses it without a particle.
So:
Words like these often do not need に:
By contrast, more specific time points often take に, such as:
So this sentence sounds natural without any particle after 来月.
Usually, 来月結婚します is the more natural choice.
With relative time words like 来月, に is generally omitted. Adding に may sound unnatural or overly marked in many normal situations.
So for a learner, the safest pattern is:
します is the polite form of する.
Japanese often uses the polite form in everyday conversation, especially with people you do not know well, in formal situations, or when speaking politely in general.
So this sentence is a polite statement.
It is built from:
Together, 結婚する acts as a verb meaning to marry / to get married.
This is a very common Japanese pattern called a suru-verb:
So grammatically, 結婚します is a noun + する, but it functions like a normal verb.
Usually, in a sentence like this, it means to get married.
Japanese often does not force the same distinction English does.
If you want to mention the person, you can use と:
Without と, the sentence simply says that the speaker is getting married.
Japanese often puts time expressions near the beginning of the sentence.
So this order is very common:
It helps set the time frame first, then gives the action.
Japanese word order is more flexible than English, but putting the time expression first is extremely natural.
Yes. In Japanese, the non-past form covers both present and future, depending on context.
Here, because 来月 means next month, the sentence clearly refers to the future.
So 結婚します here means something like:
The time word makes the future meaning clear.
Yes, that is very natural.
In writing, Japanese often uses a comma after a time expression:
The comma shows a small pause and makes the sentence easier to read. In speech, there is often a slight pause after 来月 as well.
Without the comma, the sentence is still correct:
Both are natural.
It is a complete and natural sentence.
Even though English often wants more information, Japanese does not always need to state:
If the context is already known, 来月結婚します。 is perfectly normal and complete.
It sounds like a simple announcement of a personal plan or life event.