English is a SVO language.
SVO means: Subject, Verb, Object(s) in exactly this order.
But English is the only Germanic language with this word order. German and all other Germanic languages (Dutch, Afrikaans, Yiddish, Swedish, Danish, Norwegian and many others) are V2 languages.
V2 means: Verb at position 2.
SVO is a more strict subtype of V2.
In German the subject can be almost everywhere in the sentence, and at position 1 can be really everything (except the verb).
So, all these sentences are correct German sentences and they are used by German native speakers:
- Mein Bruder spielt manchmal Klavier.
- Manchmal spielt mein Bruder Klavier.
- Klavier spielt mein Bruder manchmal.
- Klavier spielt manchmal mein Bruder.
Example #2 also answers your question: Since everything can be at position 1, also an adverb can be there, which means, it can come before the verb.
Note also, that only the inflected verb stands at position 2. German sentences always contain a main verb and very often also an auxiliary verb (haben, sein, werden) and sometimes also a modal verb (dürfen, können, mögen, müssen, sollen, wollen). Only one of them will be inflected, and this inflected verb stands at position 2. All other verbs stand at the end of the sentence.
Morgen wird Barbara sicher nicht mit ihrem Bruder in seinem hässlichen und rostigen Auto schon um 8 Uhr morgens in die Hauptstadt fahren wollen.
Tomorrow Barbara will certainly not want to drive to the capital city with her brother in his ugly and rusty car already at 8 o'clock in the morning.
There are 3 verbs in this sentence (marked bold). But only one of them (»wird«, a form of the auxiliary verb »werden«) is inflected to match with the subject in number (singular) and person (3rd person). And only this inflected verb stands at position 2. All other verbs stand at the end.
Also note, that German has separable verbs. These are verbs that consists of two parts: The prefix and the main part. There are thousands of these verbs. What makes them special is, that this prefix can be split off from the main part and then stands at the very end of the sentence.
Here is an example: einschlafen = to fall asleep
Futur I: Jürgen wird einschlafen.
Jürgen will fall asleep.
Präsens: Jürgen schläft ein.
Jürgen falls asleep.
With some more parts in the sentence:
Jürgen schläft, soweit mir das bekannt ist, denn ich weiß das auch nur aus Erzählungen, an Freitagen und Samstagen niemals vor 22 Uhr ein.
Jürgen never falls asleep before 10 p.m. on Fridays and Saturdays, as far as I know, because I also only know this from stories.
In this sentence the two "words" »schläft« and »ein« in fact are two parts of one word (a verb). So, also in this sentence only the inflected part of the verb stands at position 2, anything else that is a verb or belongs to a verb is at the end.
Also note, like mentioned in some comments, this word order is only valid for statements.
In closed questions (requesting a yes/no-answer) the inflected verb stands at position 1.
Spielt dein Bruder manchmal Klavier?
Also in commands
Spielen Sie Klavier!
And in subordinate clauses all verbs (including the inflected verb) stand at the end of the sentence.
Ich habe gehört, dass dein Bruder manchmal Klavier spielt.