These firey twins can help fresh Tenno carve their way across the star chart. This build requires no forma or reactor but is effective against Grineer until level 45 and Corpus until level 40.

THE BASICS

Heat strips armor and causes targets to 'flail' for a few seconds, during which they don't attack. The 80% status chance + [Swirling Tiger]'s multiattacks + [Reach] lets you both handle crowds of enemies as well as Elites.

Slash is effective against all flesh types and several of [Swirling Tiger]'s hits do double or triple slash damage.

Without [Swirling Tiger], this build does not work. If you don't have [Drifting Contact], use [Melee Prowess].

You don't need [Reach], but it's aggravating to play without it.

THE DRAWBACKS

This does best against Grineer. Against Corpus, it can handle most enemies, but elites will waste your time as you chew through their shield.

The low crit chance and damage mean that there's no burst.

This isn't end-game viable. If you invest forma or a reactor in it, understand that eventually it will be outperformed.

UPGRADES

Melee Aura - On your Warframe. You get these through Nightwave. If you enjoy melee, it's a must-have.

Primed Pressure Point, Primed Reach - Available from the Void trainer.

Quickening, Fury, Primed Fury - To cut through enemies faster.

OTHER DAMAGE TYPES

Combined with Electric, Heat will give you Radiation Damage. This can be helpful against robotic enemies (MOA, Ospray, and some Corpus Bosses) as well as Grineer Alloy Armor (Bombarders, Napalm, and bosses like Vor or Tyl).

You could also do Viral or Corrosive + Heat, but if you have more than one status type, try to get your Status over 100%.

I would avoid Blast or Gas, as I find them less useful than plain Heat.