Most cars use high-strength steel for the structure, aluminum for body panels, plus smaller amounts of magnesium, stainless steel, and copper.
What Metals Are Used In Car Bodies Today
Peek beneath the paint and you’ll find a smart blend. Engineers mix grades of steel, several families of aluminum, a dash of stainless, and just enough copper and magnesium to run and protect everything. Cast iron still shows up in brakes and some engines, while rare parts on performance models may turn to titanium. The mix shifts by brand and powertrain.
Where Each Metal Usually Goes
| Vehicle Area | Common Metals / Alloys | Why Used |
|---|---|---|
| Body-in-white (pillars, rails, rockers) | High-strength steel, AHSS, press-hardened steel | Crash energy control, stiffness, weldability, cost control |
| Outer panels (hood, doors, fenders) | Aluminum 5xxx/6xxx sheet; some steel | Lower mass for better range or mpg; dent resistance with age-hardening |
| Closures & crash beams | Ultra-high-strength steel, boron PHS; aluminum extrusions | Strong beams with tight packaging; weight savings in hinges and latches |
| Battery trays & motor housings (EV) | Aluminum castings, extrusions; some steel | Heat dissipation, corrosion resistance, light yet rigid boxes |
| Engine blocks & heads (ICE) | Aluminum castings; some compacted-graphite or gray iron | Aluminum cuts block weight; iron handles heavy duty loads and heat |
| Exhaust & underbody hot zones | Ferritic stainless (409/439), aluminized steel | Heat and salt tolerance with fair cost |
| Suspension knuckles, control arms | Aluminum castings/forgings; steel stampings | Reduce unsprung mass; tune ride and steering feel |
| Wheels | Aluminum cast/forged; steel rims on base trims | Weight drop and style options; steel for value |
| Steering wheels, seat frames | Magnesium die castings; steel stampings | Trim grams in the cabin without bulky shapes |
| Wiring, busbars, motors | Copper and copper alloys | Top-tier conductivity for power and signals |
| Fasteners & small brackets | Carbon steel, stainless; some aluminum | Strength where needed; corrosion protection with coatings |
Modern bodies also rely on coatings. Most stamped steel panels carry zinc-rich galvanizing, and the whole shell runs through pretreatment, e-coat, primer, and paint. Aluminum panels form a protective oxide layer and often get shop-applied conversion coatings before paint. That layered approach keeps rust at bay for years.
What Kind Of Metal Do Cars Use By Part
Steel Family: From Mild To Ultra-High-Strength
Steel is still the backbone. You’ll see mild steel in low-load stampings, high-strength low-alloy for bracing, and advanced high-strength steel with names like dual phase, TRIP, complex phase, and martensitic. Press-hardened steel adds boron and uses hot forming to create extremely tough door rings and pillars. Learn more in the AHSS definitions from WorldAutoSteel.
Strength classes vary by maker. Many place the AHSS label at 440 MPa tensile and up, with ultra-high-strength above the 980 MPa band. The point isn’t the number; it’s the stiffness and ductility balance that lets a rocker, pillar, or ring carry loads without extra thickness. That’s why steel still owns the safety cage on most platforms.
Body engineers also use tailored blanks. That means two or more sheets with different thickness or grades are laser-welded together before stamping. The pillar or rail then places thicker, tougher steel only where loads peak, saving mass elsewhere. Hot-formed door rings push this idea even further by giving a single piece many strength zones after the oven and press. The result is tidy packaging with fewer seams and a shell that channels impact loads away from the cabin.
Aluminum Alloys: Panels, Castings, And Extrusions
Aluminum keeps showing up in more places. Sheet from the 5xxx and 6xxx series suits doors, hoods, and fenders. Extrusions build crash rails and battery frames. Large castings carry motor housings, inverter cases, and subframes. Automakers like the mass savings and the way 6xxx sheet age-hardens during paint bake for sharper dent resistance. Independent surveys point to rising pounds per vehicle as electrified models add big housings and heat-spreading trays. See the Aluminum Association summary on rising content per vehicle.
Not all sheets act the same. 5xxx alloys resist corrosion and suit simple shapes like roofs and trunk lids. 6xxx alloys stretch and form deep panels, then gain strength during the paint-bake step. Extrusions shine where straight, box-like rails can add crash space without bulky stampings. Castings pack complex geometry, cooling passages, and threaded inserts into one piece that drops right on the line.
Magnesium Where Grams Matter
On a build line, aluminum often uses rivets, flow-drill screws, MIG welds, and structural adhesives with isolators at mixed joints.
Stainless Steel In Hot Zones
Exhaust parts live tough lives, so ferritic stainless grades such as 409 and 439 are common picks. They shrug off road salt and high heat at a price point that suits mass production. Catalytic converters, mufflers, and tailpipes often blend stainless with aluminized steel to balance durability and cost.
Magnesium Where Grams Matter
Magnesium castings trim weight in steering wheels, seat structures, and some housings. The metal is light and stiff for its mass, which helps with packaging and feel. It’s more niche than aluminum due to price, corrosion control, and formability limits, yet it’s handy in spots where every gram counts.
Cast Iron Still At Work
Brake rotors are usually gray iron for heat capacity and wear. Engine blocks in heavy-duty or turbo-dense applications may use compacted-graphite or traditional gray iron for strength and stability. Many passenger engines moved to aluminum blocks and heads long ago to cut weight, but iron remains a trusted choice when thermal loads run high.
Copper For Power And Signals
Copper carries current with minimal loss. Wire harnesses, motor windings, inverters, radiators, and heaters all draw on it. Even a non-hybrid holds dozens of sensors and control modules tied together by kilometers of copper wire. EVs add more copper mass in high-voltage cables and motors.
A typical gas car can carry several dozen pounds of copper once you count wiring, motors, and heat exchangers. Battery-electric models often need far more for busbars, drive motors, and charging gear. That extra copper helps manage heat and keeps voltage drop in check across the pack and power electronics.
Titanium And Other Specialty Metals
Track-focused models sometimes use titanium for intake valves, connecting rods, or exhaust parts to save reciprocating mass and resist heat. The alloy Ti-6Al-4V shows up the most in those roles. It’s rare in daily drivers, yet it proves how targeted metal swaps can unlock performance.
Why So Much Steel In A Modern Car
Steel delivers a sweet trio: strength, predictable forming, and sensible cost. Body shells need crisp folds, spot-welded seams, and reliable crash performance across tens of thousands of units. That’s where AHSS and press-hardened parts shine. North American stats peg steel at a little over half the average vehicle’s mass, with the rest spread across aluminum, polymers, glass, and the electrical bits.
On the road, less mass helps any powertrain. The U.S. Department of Energy notes that trimming vehicle weight can lift fuel economy in conventional models and stretch range in EVs. Their overview of lightweight materials for cars and trucks also lists the common metals automakers swap in to save weight while keeping safety steady.
There’s also a supply chain angle. Steel mills, stampers, and weld lines already run at giant scale with short cycle times. That makes it easier to meet tight launch dates and keep panel gaps consistent across plants. Steel scrap from stamping goes straight back into the loop, which helps factories cut waste and keeps material steady.
Aluminum’s Rise With Hybrids And EVs
Electric layouts add battery packs, cooling, and power electronics. To avoid a mass spiral, engineers pull weight back out with aluminum sheet, extrusions, and large castings. Doors and hoods move to 6xxx sheet. Battery enclosures lean on extrusions and cast nodes. Motor housings and drive-unit cases are almost always cast aluminum. Across surveys, battery-electric models tend to carry far more aluminum than comparable gas cars, largely due to those housings and crash-energy rails around the pack.
The switch brings side benefits. Aluminum resists corrosion, conducts heat well, and can simplify parts with casting and extrusion integration. That’s why you’ll see one-piece rear castings or multi-chamber battery trays where steel would need many spot-welded pieces. Repair shops adapt with new rivets, adhesives, and isolation steps to avoid galvanic issues where aluminum meets steel.
Battery trays also act as heat sinks and fire barriers. Extrusions form tall, multi-chamber rails that vent and route air, while cast corners tie everything together. The goal is a stiff, sealed box that shields cells and manages heat without adding bulk.
Corrosion Protection And Paint Stacks
Bare steel would rust fast, so automakers start with zinc-coated sheet. Galvanizing forms a sacrificial barrier that shields cut edges and seams. After welding and assembly, the body dips through phosphates and an epoxy e-coat bath that creeps into seams. Primer and topcoat finish the shell. Aluminum panels form a tough oxide layer and often get conversion coatings before paint to improve adhesion. Stainless in the exhaust needs no paint, while fasteners and brackets use durable coatings.
Higher-end lines add underbody sealers, waxes in cavities, and thicker wheel-arch liners. In salty climates, regular rinses help, especially after a snowstorm.
Metal Picks That Match The Goal
Every vehicle floats between safety targets, range or mpg, styling space, and wallet realities. Material choices follow those goals. The list below sums up where each metal tends to win.
Quick Selector: Metal Vs. Design Goal
| Design Goal | Metals That Fit | Notes From The Field |
|---|---|---|
| Crash performance with lean mass | AHSS, press-hardened steel; aluminum extrusions | Thin gauges with high strength; tailored blanks and hot-formed rings |
| Range and energy efficiency | Aluminum sheet/castings; magnesium in small parts | Lower curb weight helps any powertrain; EVs gain extra miles |
| Heat and corrosion near exhaust | Stainless 409/439; aluminized steel | Handles salt and hot cycles without heavy shields |
| Fast stamping and low part cost | Mild and HSLA steels | Stable forming windows and simple joining on high-rate lines |
| Compact, integrated housings | Aluminum castings | One piece can replace many stampings and welds |
| High-rev powertrain parts | Titanium on exotic builds | Shaves reciprocating mass; priced for specialty runs |
| Electrical power delivery | Copper | Low resistance keeps heat down and systems efficient |
What Types Of Metal Are Cars Built With In 2025
Across showrooms, the mix looks like this. A typical sedan or crossover leans on steel for the safety shell, sprinkles aluminum into closures and suspension, uses iron for rotors, and carries a few dozen pounds of copper for wiring. A battery-electric model piles on more aluminum in the body-in-white, the battery tray, and the drive unit. Trucks and SUVs often add thicker gauges and higher strength grades to manage towing and payload while keeping weight in check. Luxury brands may add cast or forged subframes for ride feel.
Regional flavor matters too. North American makers adopt AHSS heavily in pillars and rockers, while European models often run higher aluminum content in closures. EV startups that build megacast rear structures lean toward aluminum around the battery and motors. Each path chases the same outcome: safety, range, and quiet cabins without bloat.
Maintenance And Ownership Notes
Knowing what’s under the paint helps with care. Door dings on 6xxx aluminum panels need techs who can work heat and access points. Mixed-metal joints like steel-to-aluminum require proper isolators during repair to avoid galvanic issues. Winter-driven cars appreciate regular rinses to clear salt from seams and underbody pockets. Exhaust parts in stainless tend to outlast the rest of the car, while iron rotors like a periodic clean pass to strip surface rust if the car sits.
Stick with pH-balanced cleaners on bare aluminum under-hood parts, and rinse engine bays gently. If you tinker, protect ground points after service so coatings aren’t scraped away. Keep drain holes in rockers open; pooled water is the sworn enemy of any metal shell.
Key Takeaways You Can Use Today
- Steel still carries the safety cage thanks to modern AHSS and PHS grades today.
- Aluminum saves weight in doors, hoods, battery trays, motors, and crash rails.
- Stainless lives in the hot zones; iron anchors rotors; copper keeps electrons moving.
- Magnesium trims small parts where packaging is tight.
- Titanium shows up on specialty builds that chase lap times.
- Coatings and paint stacks matter as much as the base metal for long life.