Mi metas la buteron sur la panon.

In Esperanto, verbs do not change according to the subject the way they do in many European languages. The ending -as always means present tense, no matter who is doing the action.

So:

• mi metas = I put / I am putting
• vi metas = you put / you are putting
• li metas = he puts / he is putting

The word mi already tells you that the subject is I, so the verb does not need a special I form.

La is the Esperanto word for the. It does not change for gender, number, or case.

So here:

• la buteron = the butter
• la panon = the bread

Esperanto often uses la in much the same way English uses the. If both things are specific and known in the situation, la is natural.

Esperanto has no indefinite article. There is no separate word for a or an.

So:

• butero can mean butter or a butter depending on context
• pano can mean bread or a loaf/piece of bread, depending on context

If you say la buteron, that is specifically the butter. If you leave out la, it becomes more like butter / some butter.

The -n marks the direct object. That is the thing directly affected by the verb.

Here, the thing being put is the butter, so:

• Mi metas la buteron = I put the butter

A very common Esperanto pattern is:

• subject
• verb
• direct object marked with -n

So buteron has -n because it is what is being moved or placed.

This is one of the most important things to notice in the sentence.

Normally, a preposition like sur means on. But when Esperanto wants to show movement toward a place, it can add -n to the noun after the preposition.

So:

• sur la pano = on the bread, at that location
• sur la panon = onto the bread, toward that surface

In this sentence, the butter is being moved onto the bread, so sur la panon is very natural.

The difference is mainly:

• sur la pano = on the bread as a location
• sur la panon = onto the bread as a destination

Compare:

• La butero estas sur la pano. = The butter is on the bread.
• Mi metas la buteron sur la panon. = I put the butter onto the bread.

English often uses on for both ideas, but Esperanto can show the difference more clearly with -n.

By itself, sur basically means on.

But in actual sentences:

• sur + no -n often gives the idea of on
• sur + -n often gives the idea of onto

So in practice:

• sur la tablo = on the table
• sur la tablon = onto the table

That is why sur la panon can be understood as onto the bread.

The normal, most neutral order is:

• Mi = subject
• metas = verb
• la buteron = direct object
• sur la panon = prepositional phrase

So Mi metas la buteron sur la panon is the most straightforward order.

Esperanto word order is fairly flexible because endings like -n show the grammatical role. But beginners should usually stick to the normal order unless there is a reason to emphasize something.

Yes, you could, but the meaning changes.

• Mi metas la buteron sur la panon = I put the butter on the bread
• Mi metas buteron sur panon = I put butter on bread / I put some butter on some bread

Without la, the sentence sounds less specific and more general.

In Esperanto, pano can often be used in a broad way, much like English bread in everyday speech.

So sur la panon can naturally mean on the bread in a simple learner sentence. Context tells you what kind of bread is meant.

If you want to be more specific, you can say things like:

• pantranĉaĵo = slice of bread
• tranĉaĵo de pano = slice/piece of bread

But for a basic sentence, pano is completely normal.

Yes. Meti is a very common Esperanto verb meaning to put, to place, or to set.

So:

• Mi metas la libron sur la tablon. = I put the book on the table.
• Ŝi metas la tason en la ŝrankon. = She puts the cup into the cupboard.

It is one of the standard verbs you will see again and again in beginner Esperanto.