These two words, although pronounced the same, have unrelated meanings.
Steel is a kind of metal, an alloy (a mixture of metals) consisting mainly of iron, and smaller amounts of other metals, such as carbon, which gives steel its useful combination of strength, flexibility, and resistance to corrosion.
Steel is most commonly a noun, but steel can also be used as an adjective or verb referring to these qualities (hardness, strength, flexibility, and un-corruptablity):
- Modern buildings and machinery would be impossible without steel. (noun)
- He has nerves of steel. (a cliché)
- Steel knives do not rust as quickly as ones made of pure iron. (adjective)
- She steeled herself (made herself feel strong and hard) to face her enemies. (verb)
Often, we use the adjective form steely when talking about things that are not literally steel:
She met her opponents with a steely look on her face.
And of course this discussion would be in complete without mentioning "The Man of Steel"—Superman’s sobriquet (fancy nickname).
Now, steal is a completely different story. It is used mainly as a verb (steal, stole, stolen) , which means ‘to take something which belongs to someone else, wrongfully’:
- Hollywood movie-makers steal a lot of ideas from older films, without giving credit.
- The robbers stole the gold from the bank.
However, strangely, the noun steal does not mean this; it means ‘a good deal, a bargain’ – i.e. something that one can buy, rightfully, at a price so low that it feels like stealing:
- The child’s mother stole into the room silently to look at her sleeping children.
- The prisoners planned to escape by stealing away in the dead of night.
Steal has many great metaphorical meanings, which appear in set phrases:
- He stole a kiss when she turned her head. (to kiss someone quickly, without permission).
- She stole a moment to eat before class. (to find a free moment, between obligations).
- That actor always steals the show. (to get all of the audience’s attention in a performance).
- The president did not steal the election. (to ‘win’ an election illegally, not by the vote)
...and many others; apparently stealing is a very productive concept in English!