A couple of words that require the instrumental case:

tapti - tampa - to become
važiuoti - važiuoja - to go (by transport)

As said previously, nouns in the instrumental case mean that they are an instrument:

Jie važiuoja autobusu. They are going by bus.
Mes važiuojame traukiniu. We are going by train.
Visada važiuok tramvajumi! Always go by tram!

A road can also be interpreted as an instrument in Lithuanian:

Jie važiuoja gatve. They are driving on the street.
Mes einame šaligatviu. We are walking on the pavement.
Visada važiuok greitkeliu! Always drive on the highway!

What hasn't been mentioned in the previous lesson is that the nouns can also mean what the subject becomes:

Jis tampa tėvu. He becomes a father.
Ji tampa motina. She becomes a mother.
Mums reikia tapti tėvais. We need to become parents.
Transformeris tampa automobiliu. The transformer becomes an automobile.