Metals and plastics are two essential material categories used across various industries and applications, from consumer goods manufacturing to the production of technical components.
Sarah Guaglianone
Updated on June 2, 2026
A comparison of the structure and composition of the two materials, plastic and metal:
Metals have a long history in various industries, including automotive manufacturing, mechanical engineering and energy generation. These industries shaped the Industrial Revolution, when metal became the standard material of choice.
Metals consist of metallic elements with a crystalline structure. The atoms are arranged in a regular lattice, which gives them high strength, density and electrical conductivity.
The development and use of plastics began in the 19th century, but their rise to become a widely used and important material across various industries did not begin until the 1950s. Since then, they have been regarded as a cost-effective alternative to metal, glass or wood, particularly in construction, the automotive industry, packaging and electronics.
Plastics consist of long chains of molecules known as polymers. These chains can have linear, branched or cross-linked structures. When heated, these polymers are highly malleable and can be moulded into almost any desired shape. Once they have cooled and solidified, the long chains of molecules bond together, giving the plastic its strength.
There are two main types of plastics:
Metals and plastics possess a range of properties that make them suitable for numerous applications.
The malleability of materials is important for many applications for a number of reasons. These include design flexibility in product design, manufacturability in mass production, and the possibility of repairs and maintenance.
Plastics are generally more flexible and adaptable, whereas metals require more energy and time to be shaped.
In principle, components made from different materials should be able to withstand the stresses to which they are subjected, and should offer the best possible durability and efficiency.
Plastics are highly adaptable, but metals remain the first choice for extreme loads and a long service life.
So why has plastic replaced metal as a material in so many applications over the last few decades? In these respects, plastics offer numerous advantages over metals:
In general, plastics offer better shock absorption than metals, making them ideal for shock-absorbing applications such as protective covers, bumpers, protective sleeves and packaging materials.
Plastics offer improved sound-insulating properties compared to metals and can therefore play an effective role in reducing noise in buildings, vehicles and machinery, such as in machine covers and tractor fairings.
Compared to metals, plastics are more resistant to many corrosive environments. They generally do not react with water, acids or alkalis, making them ideal for use in damp environments and in chemical processes.
Plastics offer good electrical insulation properties. Examples of their use include ESD workpiece carriers, ESD transport packaging and plastic enclosures for electronics. In general, metals have very poor electrical insulation properties compared to non-conductive materials such as plastics. Metals conduct electrical current, which is why they are not suitable for use as shielding in the form of enclosures.
Plastics can be good thermal insulators, particularly when compared to metals. The thermal conductivity of plastics is generally significantly lower than that of metals, which means they conduct heat more slowly through their mass. This makes plastics effective thermal insulators in many applications.
Plastics are often less expensive than metals, both in terms of material costs and manufacturing costs.
Metals are produced through complex processes: they are made by smelting and shaping metal ores, followed by various processing methods such as casting, forging and rolling.
These processes often require high temperatures, significant energy consumption and specialised equipment, which increases production costs compared to plastics.
Plastics can be produced in large quantities at relatively low cost. Their weight reduction offers additional benefits:
Although plastic and metal are recyclable, the recycling of metals requires the use of high temperatures and therefore a very high energy input. In contrast, plastic can be shredded and reused as recycled material.
| Features | Metals | Plastics |
|---|---|---|
| Structure | Crystal | Polymer (linear, branched or cross-linked structure) |
| Cost of production | High | Low |
| Energy consumption | High | Low |
| Design options | Medium | High |
| Durability | High | High |
| Corrosion resistance | Vulnerable | Consistent |
| Strength | High | Medium |
| Stiffness | High | Medium |
| Ductility | High | Variable |
| Weight | Difficult | Light |
| Electrical conductivity | Senior | Electrical insulator |
| Heat resistance | High | Medium |
| Thermal conductivity | High | Low to medium |
| Thermal insulation | Low | High |
| Manufacturing process | Melting, casting, forging, rolling | Polymerisation, injection moulding, extrusion, thermoforming |
| Environmental impact | Extraction and processing require energy and can cause environmental damage | Plastics can be reprocessed as recycled material, but they are not biodegradable |
The choice between plastics and metals ultimately depends on the specific requirements of the application, including design requirements, functionality and cost. Both plastics and metals have their own specific strengths and weaknesses, and the right choice is made by carefully weighing up the various factors.
Plastic is a better choice than metal for more cost-effective production and offers a wider range of design options. We’d be happy to advise you! Please get in touch with formary contact to discuss any queries you may have, including the use of bioplastics in thermoforming.
Plastics are made of polymers, which have a lower density than metals. As a result, plastic components are lighter, which reduces transportation, storage, and energy costs and increases design flexibility.