I'm an electrical contractor and I was hired by two guys, everything was verbal so there is not contract signed, so now looks like they don't want to pay me for the work I did for 3 months, what can I do
Generally, when unpaid for construction work, pursuing a mechanics lien is a stong option for forcing payment. Electrical contractors are entitled to mechanics lien rights in CA when they go unpaid for their work, and that's true regardless of whether there's a written contract or simply a verbal agreement.
With that being said, in order to preserve lien rights, a preliminary notice is generally required - and that should be sent within 20 days of first furnishing labor or materials. Though, if you were hired directly by the property owner, that notice may not be required. You can learn more about the preliminary notice rules here: California Preliminary Notice Rules & FAQs.
As you mentioned above, simply threatening to file a lien claim will often be enough to get paid. More on that idea, here: What is A Notice of Intent to Lien And Should I Send One? Further, note that mechanics lien rights are only one path toward recovery. Legal claims (like breach of contract, unjust enrichment, or even under CA's prompt payment laws) should be on the table, too. And, just like with liens, threatening legal claims will often lead to payment. Further discussion here: Construction Demand Letters – How To Write One That Gets You Paid.