
das Blech
sheet metal
A thinly rolled, flat piece of metal, for example made of steel, aluminum, or copper.
Für die Autoreparatur musste ein neues Stück Blech eingeschweißt werden.
For the car repair, a new piece of sheet metal had to be welded in.
sheet metal / baking tray
Loading your saved state.

sheet metal
A thinly rolled, flat piece of metal, for example made of steel, aluminum, or copper.
Für die Autoreparatur musste ein neues Stück Blech eingeschweißt werden.
For the car repair, a new piece of sheet metal had to be welded in.

baking tray
A flat, rectangular metal tray used for baking in the oven; a baking sheet.
Sie legte die Plätzchen auf das mit Backpapier ausgelegte Blech.
She placed the cookies on the baking tray lined with parchment paper.

brass section
Colloquial term for the group of brass instruments in an orchestra or band.
Bei diesem Stück hat das Blech einen sehr kraftvollen Einsatz.
In this piece, the brass section has a very powerful entrance.

to talk nonsense
Colloquial for talking nonsense or saying stupid stuff.
Hör auf, so ein Blech zu reden, das stimmt doch gar nicht!
Stop talking such nonsense, that's not true at all!
The meaning of 'Blech' depends heavily on the context. In a workshop it means metal, in the kitchen a baking tray, and in an orchestra the brass instruments.
Der Mechaniker bestellte ein neues Blech für die Autotür.
The mechanic ordered a new piece of sheet metal for the car door.
In a craft or workshop context, 'Blech' (sheet metal) is often used with verbs that describe processing or working the material. Typical combinations are 'Blech schneiden' (to cut sheet metal), 'Blech biegen' (to bend sheet metal), or 'Blech schweißen' (to weld sheet metal).
Der Handwerker muss das Blech genau auf die richtige Größe zuschneiden.
The craftsman has to cut the sheet metal exactly to the right size.
In a kitchen context, prepositions that describe position or movement are important. You put something 'aufs Blech' (onto the baking tray) or take something 'vom Blech' (off the baking tray).
Für die Pizza streiche ich die Tomatensoße direkt aufs Blech.
For the pizza, I spread the tomato sauce directly onto the baking tray.
The expression 'Blech reden' (to talk nonsense) is a fixed colloquial phrase and means 'Unsinn erzählen' (to tell nonsense). The word 'Blech' is used for this meaning only in this combination.
Er hat den ganzen Abend nur Blech geredet.
He talked nothing but nonsense all evening.
plate / record
Platte and Blech can both refer to a flat piece of metal. Blech is typically thin and rolled; Platte refers more often to a separate, rigid, and usually thicker piece. Thickness and rigidity are therefore the main factors in choosing between them.

Für die leichte Abdeckung verwendet die Werkstatt ein dünnes Blech.
The workshop uses a thin sheet of metal for the lightweight cover.
Für den stabilen Boden verwendet die Werkstatt eine dicke Metallplatte.
The workshop uses a thick metal plate for the sturdy base.