der Eimer
bucket
A cylindrical container with a handle, used for carrying liquids or solid materials such as sand or water.
Füll bitte den Eimer mit Wasser.
Please fill the bucket with water.

bucket
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bucket
A cylindrical container with a handle, used for carrying liquids or solid materials such as sand or water.
Füll bitte den Eimer mit Wasser.
Please fill the bucket with water.

In its basic meaning, 'Eimer' (bucket) is often combined with verbs that describe an action involving a container. Typical phrases are 'einen Eimer füllen' (to fill a bucket), 'einen Eimer leeren' (to empty a bucket), or 'einen Eimer tragen' (to carry a bucket).
Kannst du bitte den Eimer mit Sand füllen?
Can you please fill the bucket with sand?
The colloquial expression 'im Eimer sein' (to be ruined/broken) is fixed. The subject of the sentence is the thing that is broken, followed by a form of 'sein' (to be) and the expression 'im Eimer' (ruined/broken).
Mein Handy ist ins Wasser gefallen und jetzt ist es komplett im Eimer.
My phone fell into the water and now it's completely ruined.
The idiom for heavy rain has a fixed structure: the subject is always 'es' (it), and the verb is 'schütten' (to pour). The expression 'wie aus Eimern' (as if from buckets) remains unchanged.
Nimm einen Schirm mit, es schüttet wie aus Eimern!
Take an umbrella with you, it's pouring down!
container
'Eimer' and 'Behälter' both refer to things that you can put or pour something into. But an 'Eimer' is a specific type of container: usually round, open, and with a handle, for example for water, sand, or cleaning products. 'Behälter' is more general. A container can have many shapes and be made of glass, plastic, or metal. Learners may confuse the words because every 'Eimer' is a 'Behälter', but not every 'Behälter' is an 'Eimer'. If the shape with a handle is important, you say 'Eimer'. If only the function is important, 'Behälter' fits.

Das Kind trägt im Garten einen Eimer voll Sand.
The child is carrying a bucket full of sand in the garden.
Zum Aufbewahren der Schrauben stellt David einen kleinen Behälter ins Regal.
To store the screws, David puts a small container on the shelf.